Mana System

This campaign replaces the standard D&D 5E spell slot system with a mana-based magic system. However, each of the four magic systems accesses and uses mana in fundamentally different ways, reflecting their unique natures.

Overview

While all magic systems use the concept of "mana" as a resource, the mechanics differ dramatically:

Arcane Magic: Simple mana pool that builds up in the caster's aura
Divine Magic: Unlimited power source with harsh daily limits and consequences
Fae Magic: Traditional spell slots granted by relationships with fey and elemental entities
Infernal Magic: Unknown limits accessed through demon pacts, with severe consequences for overuse

Arcane Mana

Arcane magic is the simplest mana system. Casters build up arcane magic in their aura and expend it on spells and enchantments.

Core Mechanics

Mana Pool: Arcane casters have a pool of mana points that represents magical energy stored in their aura
Mana Cost: The mana cost of a spell is equal to the spell's level. Casting a 2nd level spell costs 2 mana
Upcasting: Spells cast at higher levels require one additional mana point for each additional level above the base level
Cantrips: Use a negligible amount of mana and do not deduct from mana points
Recovery: 100% of mana recovers after a long rest

Determining Arcane Mana

Arcane mana is based on base mana plus Intelligence modifier multiplied by caster level.

Mana Calculation: Base Mana + (Intelligence Modifier × Caster Level)

Arcane Caster Level	Base Mana	Mana Formula	Max Spell Level
1	1	1 + (INT mod × 1)	1st
2	2	2 + (INT mod × 2)	1st
3	6	6 + (INT mod × 3)	2nd
4	8	8 + (INT mod × 4)	2nd
5	13	13 + (INT mod × 5)	3rd
6	16	16 + (INT mod × 6)	3rd
7	20	20 + (INT mod × 7)	4th
8	24	24 + (INT mod × 8)	4th
9	31	31 + (INT mod × 9)	5th
10	36	36 + (INT mod × 10)	5th
11	43	43 + (INT mod × 11)	6th
12	46	46 + (INT mod × 12)	6th
13	50	50 + (INT mod × 13)	7th
14	54	54 + (INT mod × 14)	7th
15	58	58 + (INT mod × 15)	8th
16	60	60 + (INT mod × 16)	8th
17	68	68 + (INT mod × 17)	9th
18	72	72 + (INT mod × 18)	9th
19	78	78 + (INT mod × 19)	9th
20	86	86 + (INT mod × 20)	9th

Example: A 10th level wizard with Intelligence 18 (+4 modifier) has 36 + (4 × 10) = 76 mana points.

Arcane Spell Access

All Arcane Casters: All arcane classes have access to all spells they know without preparation.

Wizards: Know spells from their spellbook. You know a number of wizard spells equal to Intelligence modifier + wizard level (minimum 1). Spells must be of a level you can cast.
Sorcerers: Know spells innately. You know a number of spells equal to Charisma modifier + Sorcerer level.
Artificers: Know spells from the Artificer spell list. You know a number of spells equal to Intelligence modifier + half Artificer level (rounded down).
No Preparation Required: All known spells are available to cast at any time (subject to mana limits and spell level restrictions).

Arcane Spell Limitations

Can only cast spells you know from your class spell list
Cannot cast spells above your maximum spell level
Cannot exceed your mana pool

Arcane Recovery

Mages can use Arcane Recovery to recover mana. Recover mana equal to Mage level + Intelligence modifier.

Example: A 10th level mage with Intelligence 18 (+4 modifier) can recover 10 + 4 = 14 mana points.

Divine Mana

Divine magic comes directly from the gods and has no technical limit to the amount of mana available. However, mortal bodies cannot handle unlimited divine power, creating harsh limits on usage.

Core Mechanics

Unlimited Source: Divine power is infinite—the gods grant as much as needed
Daily Limit: Divine casters have a daily threshold they can safely use
Exceeding Limits: Going over the limit causes exhaustion and the burned condition
Instant Limit: There is also a limit on how much divine mana can be channeled in a single spell or action

Determining Divine Mana Limits

Daily Limit: Divine caster level × Wisdom modifier

Instant Limit (per spell/action): Proficiency Bonus + Wisdom modifier (or alternate spellcasting ability modifier for specific classes, such as Charisma for Bards)

The instant limit represents how much divine power a caster can safely channel in a single spell or action before the divine energy begins to burn them.

Consequences of Overuse

When a divine caster exceeds their daily limit:

First Over:** Gain 1 level of Exhaustion
Second Over: Gain 1 level of Exhaustion + Burned condition
Third Over: Gain 1 level of Exhaustion + Burned condition worsens
Additional Overages: Continue gaining Exhaustion levels

When a divine caster exceeds their instant limit on a single spell:

Immediate: Take fire damage equal to excess mana used (d6 per point over limit)
Condition: Gain the Burned condition
Visual: Divine energy visibly burns the caster—radiant flames may erupt
Healing Restrictions: Divine burns cannot be healed through divine magic. They can only be healed through:
Fae Magic: Fae healing spells can heal divine burns normally
Natural Recovery: Burns heal naturally over time (recovery rate as per Burned condition rules)

Divine Spell Lists

Basic Divine Spells: All divine casters receive these spells regardless of deity: - Core healing, protection, and smiting spells (GM determines full list) - These are granted by divine magic itself, not specific deities

Domain Spells: In addition to basic spells, divine casters receive domain spells based on their patron deity: - Each deity grants specific spells appropriate to their portfolio - These spells reflect the god's nature and interests - See Divine Index for deity-specific spell lists

Divine Spell Access

All Divine Casters: All divine classes have access to all spells they know without preparation.

Clerics: Know all cleric spells of levels they can cast. Clerics know a number of cleric spells equal to Wisdom modifier + cleric level (minimum 1) from the cleric spell list.
Paladins: Know all paladin spells of levels they can cast. Paladins know a number of paladin spells equal to Wisdom modifier + half paladin level (minimum 1) from the paladin spell list.
Domain Spells: Domain spells are always known and available (in addition to base spells known).
No Preparation Required: All known spells are available to cast at any time (subject to daily/instant limits and spell level restrictions).

Recovery

Divine casters recover their daily mana limit after a long rest. They also recover 50% after a short rest spent in prayer or meditation.

Fae Mana (Spell Slots)

Fae magic behaves differently from the other systems—it uses traditional D&D 5E spell slots. This is because Fae magic is not drawn from an internal pool, but granted through relationships with fey and elemental creatures.

Core Mechanics

Relationship-Based: Fae magic comes from pacts and relationships with:
Fey creatures (fairies, dryads, sprites, etc.)
Elemental entities (elementals, nature spirits)
Natural forces (trees, rivers, mountains, etc.)
Daily Boons: Each relationship grants specific boons of power in the form of spell slots
Standard Spell Slots: Use standard D&D 5E spell slot progression per class
Safest System: Fae magic is the safest to use—no risk of exhaustion, burning, or corruption

How Fae Magic Works

Daily Grants: Each day, your fey and elemental relationships grant you spell slots: - The stronger the relationship, the more powerful slots granted - Relationships with multiple entities can grant additional slots - Relationships can be strengthened through roleplay, gifts, or quests

Spell Access: Fae casters know spells based on their relationships: - Each relationship grants access to specific spells - Druids have relationships with nature itself - know all druid spells of levels they can cast - Rangers may have relationships with specific animal or plant spirits - know all ranger spells of levels they can cast - Bards may form relationships with fey through music or stories - know all bard spells of levels they can cast - No Preparation Required: All known fae spells are available to cast at any time (subject to spell slot availability)

Fae Spell Slot Progression

Fae magic uses traditional D&D 5E spell slots. All fae casters use the half caster spell slot progression as the default. This base progression can be supplemented through roleplaying with fae creatures or through feats.

Fae Caster Level	1st	2nd	3rd	4th	5th
1st-2nd	3	-	-	-	-
3rd-4th	4	2	-	-	-
5th-6th	4	3	-	-	-
7th-8th	4	3	2	-	-
9th-10th	4	3	3	-	-
11th-12th	4	3	3	-	-
13th-14th	4	3	3	1	-
15th-16th	4	3	3	2	-
17th-18th	4	3	3	3	1
19th-20th	4	3	3	3	2

Note: This is the base progression. Additional spell slots can be gained through: - Roleplaying with Fae Creatures: Forming relationships with fey entities through quests, gifts, and interactions can grant additional spell slots - Feats: Certain feats may grant additional spell slots or improve slot progression - The GM determines what additional slots are granted based on relationships and character development

Fae Spell Slot Recovery

Spell slots granted by fey relationships recover: - Short Rest: Recover spell slots equal to half your Fae caster level (rounded up) - Long Rest: Recover all spell slots

Building Relationships

Fae casters can form new relationships through: - Extended interaction with fey creatures - Protecting natural areas - Completing quests for fey entities - Making offerings or establishing shrines - Roleplay and character development

Stronger relationships grant: - Higher level spell slots - Access to more powerful spells - Additional spell slots per day - Special abilities or boons

Fae Mana (Pool)

Some martial subclasses gain Fae magic but cannot cast spells. Instead of spell slots, their daily boons are converted into a Fae Mana pool — a single resource that powers class abilities (Spell-Like Abilities, Rage-Like Abilities, Bending Techniques, Mutations, etc.).

Conversion Formula

The Fae Mana pool is derived from the spell slot progression the subclass would otherwise receive:

Total Fae Mana = Σ (slot count × slot level)

For example, at a level where the character would have 4×1st + 3×2nd + 2×3rd slots: (4×1) + (3×2) + (2×3) = 4 + 6 + 6 = 16 Fae Mana.

This is consistent with the cross-system equivalence rule: 1 spell slot level = 1 mana point (e.g., a 3rd-level slot = 3 mana).

Half-Caster Fae Mana Progression

Used by: Monk (Way of the Wild Walker), Artificer (Biomancer / Mutagenist).

Level	Fae Mana Pool	Short Rest Recovery
1–2	3	1
3–4	8	2
5–6	10	3
7–8	16	4
9–10	19	5
11–12	19	6
13–14	23	7
15–16	27	8
17–18	34	9
19–20	39	10

Third-Caster Fae Mana Progression

Used by: Barbarian (Path of the Wild Wrath).

Level	Fae Mana Pool	Short Rest Recovery
1–2	2	1
3	3	2
4	5	2
5	5	3
6	7	3
7–8	7	4
9–12	10	5–6
13–20	14	7–10

Fae Mana Recovery

Short Rest: Recover Fae Mana equal to half your class level (rounded up)
Long Rest: Recover all Fae Mana

Restrictions

No Spellcasting: Fae Mana cannot be used to cast spells. It exclusively powers class abilities (Spell-Like Abilities).
Not Spell Slots: Fae Mana users do not benefit from features or items that interact with spell slots specifically.
Aura: Using Fae Mana still contributes to a character's Fae Aura for detection/interaction purposes. Each point of Fae Mana spent adds 1 to the character's current Fae Aura.

Infernal Mana

Infernal magic has no technical daily limit—infernal power wants to be used and will flow as long as the caster can handle it. However, this comes with severe risks and consequences.

Core Mechanics

Unlimited Source: Infernal magic has no maximum daily capacity
Unknown Limits: The player does NOT know their tolerance threshold
Pact-Based: Infernal power is accessed through pacts with demonic entities
Per-Spell Limits: Each spell has a tolerance threshold—exceeding it causes severe consequences
Chaotic and Dangerous: Infernal magic is inherently unstable

Determining Infernal Tolerance

Base Tolerance per Spell: Constitution modifier + Infernal caster level

Pact Negotiation: Charisma modifier is used when: - Forming new pacts with demonic entities - Renegotiating existing pacts - Persuading demons to grant additional power - Social interactions with infernal entities

Hidden Mechanic: The GM tracks the caster's actual tolerance, which may vary: - Base tolerance (CON-based) can be modified by: - Number of active pacts - Recent infernal magic usage - Corruption level - Specific demonic entities involved - Players must discover their limits through play - Charisma helps form pacts, but doesn't affect tolerance directly

Infernal Spell Access

All Infernal Casters: All infernal classes have access to all spells they know without preparation.

Warlocks: Know spells granted by their demonic pacts. Each pact provides access to specific spells from the warlock spell list.
Occultists: Know spells based on their Occultist level + Charisma modifier. They use the Tolerance system similar to Warlocks but with different class features.
No Preparation Required: All known infernal spells are available to cast at any time (subject to tolerance limits and spell level restrictions).

Infernal Pacts

Each demon pact grants: - Specific Spells: The demon provides access to particular spells - Increased Power: Each pact increases the caster's Available Infernal Power (AIP) - Additional Spells: New pacts unlock new spell options - Risk: More pacts = more power but also more corruption risk

Discovering Your Limits

Players can attempt to learn their limits through:

Knowledge Infernallia Checks (DC varies): - Intelligence (Infernallia) checks help you understand your limits - DC 15: Gain general sense if you're approaching a limit - DC 20: Learn approximate tolerance for spells of a specific level (based on CON + caster level) - DC 25: Precise tolerance for current conditions - Advantage: If you have relevant feats or features

Feats and Features: - Certain feats may grant insight into infernal limits - Class features may provide warnings - Magic items might monitor infernal power usage

Experimentation: - Casting spells and observing effects - Noting when consequences occur - Tracking patterns over time

Consequences of Overuse

When a caster exceeds their tolerance on a single spell, they suffer severe effects. Roll on the Infernal Overuse table:

Infernal Overuse Consequences

d20	Primary Effect	Secondary Effects
1-3	Direct Damage: Take necrotic damage equal to 2d10 per point over tolerance	Roll on Secondary Effects table
4-6	Condition: Gain one condition from: Blinded, Deafened, Frightened, or Stunned (duration: 1 hour)	Nearby creatures within 10 feet take 1d6 fire damage
7-9	Exhaustion: Gain 1 level of Exhaustion	Spell creates uncontrolled infernal effects (GM determines)
10-12	Corruption: Gain a minor mutation (see Mutation table)	All creatures within 20 feet make Wisdom saving throws or gain Frightened condition
13-15	Severe Damage: Take 3d10 necrotic damage + 2 levels of Exhaustion	Spell backfires—targets random creature within 30 feet
16-18	Major Mutation: Gain a significant mutation (see Mutation table)	Create a zone of infernal corruption (10-foot radius, 1 hour duration)
19-20	Catastrophic Failure: Take 5d10 necrotic damage, gain 2 levels of Exhaustion, and major mutation	Spell fails completely, all creatures within 30 feet take 2d10 fire damage

Secondary Effects (when triggered): - Roll d6: 1. Nearby allies gain Frightened condition 2. Infernal flames erupt in random location (10-foot radius) 3. Temporary portal to Lower Planes opens (closes after 1 round) 4. Caster's voice becomes demonic for 1 hour 5. All metal within 20 feet becomes hot to touch 6. Wild magic surge (roll on wild magic table)

Infernal Mutations

When a caster gains a mutation, roll on the appropriate table:

Minor Mutations (can be removed with greater restoration): 1. Eyes glow red in darkness 2. Small horns appear 3. Fingers become slightly clawed 4. Skin takes on slight reddish tint 5. Breath smells of sulfur 6. Voice has slight echo

Significant Mutations (requires wish or divine intervention): 1. Large horns grow from head 2. Tail sprouts (3 feet long) 3. Skin becomes scaly or leathery 4. Eyes become solid red or black 5. Fangs replace normal teeth 6. Hands become clawed permanently

Major Mutations (permanent without extreme measures): 1. Wings (bat-like, 10-foot wingspan) 2. Demon-like appearance (obvious infernal nature) 3. Constant infernal aura (damages nearby plants) 4. Cannot enter consecrated ground 5. Vulnerable to radiant damage 6. Must consume souls or suffer penalties

Infernal Spell Recovery

Infernal mana doesn't have a daily limit, but casters may suffer from accumulated corruption or exhaustion from overuse. Recovery:

Short Rest: Recover from exhaustion normally, but corruption remains
Long Rest: Recover from exhaustion, but mutations persist
Corruption Recovery: Mutations require specific spells or quests to remove

Warlock Special Rules

Warlocks use infernal mana differently:

Pact Magic: Each pact grants specific spell slots that refresh on short or long rest
Eldritch Invocations: May grant additional infernal powers
Multiple Pacts: Warlocks can have multiple demonic pacts, each adding to Available Infernal Power

Multiclassing and Mana

When multiclassing between different magic systems, casters may accumulate different types of mana in their aura. The Circle of Interaction applies to mana stored in the caster's aura, creating both opportunities and dangers.

Mana in the Aura

When a multiclass character casts spells from multiple systems, mana accumulates in their aura: - Each magic system generates its own type of mana - Mana pools are tracked separately, but all mana exists in the same aura - The Circle of Interaction affects how different mana types interact within the aura

Circle of Enhancement: Using Different Mana Types

Casters can use mana from an enhancing system to empower their spells:

Arcane → Infernal (Enhancement)

Infernal casters can use Arcane mana to empower their infernal spells
When casting an infernal spell, you can expend arcane mana instead of (or in addition to) infernal tolerance
Effect: Reduce infernal tolerance cost by the arcane mana spent, or add arcane mana to increase spell effectiveness
Risk: Still requires infernal tolerance check, but arcane mana can help buffer the cost

Example: A Warlock 5 / Wizard 3 casts Fireball (3rd level) using infernal magic. They can spend 3 arcane mana instead of using 3 infernal tolerance, or spend 1 arcane mana + 2 infernal tolerance to split the cost.

Infernal → Fae (Enhancement)

Fae casters can use Infernal mana (from recent infernal magic use, or from infernal radiation) to empower fae spells
When casting a fae spell, infernal mana in the aura can enhance it
Effect: Expend a fae spell slot, then add infernal mana to enhance the spell (roll on enhancement unstable results table)
Safe Conversion: Converting infernal mana to fae magic is one of the only safe ways to use infernal mana. Fae casters do not suffer infernal corruption, tolerance checks, or mutations when using infernal mana to enhance fae spells

Example: A Druid 5 / Warlock 3 casts Call Lightning (3rd level). They use a 3rd level fae spell slot, then can spend up to 3 infernal mana (from recent warlock spell) to enhance it. No tolerance check required—the fae magic safely channels the infernal energy.

Fae → Divine (Enhancement)

Divine casters can use Fae mana (from unused spell slots or fey relationships) to empower divine spells
Fae mana can be converted to enhance divine spells
Effect: For each fae spell slot level converted, reduce the divine mana cost by 1 (minimum 0)
Benefit: Helps stay within divine daily/instant limits

Example: A Cleric 5 / Druid 3 casts Cure Wounds (1st level). They can expend a 1st level fae spell slot to cast it, reducing divine mana cost by 1. This doesn't count against divine daily limit.

Divine → Arcane (Enhancement)

Arcane casters can use Divine mana to empower arcane spells
When casting an arcane spell, divine mana can enhance it
Effect: Expend arcane mana normally, then add divine mana to enhance (roll on enhancement unstable results table)
Important: Divine mana used for enhancement doesn't count against daily limit (but still watch instant limit)

Example: A Wizard 5 / Cleric 3 casts Fireball (3rd level). They spend 3 arcane mana, then can add up to 3 divine mana to enhance it. The divine mana doesn't count against daily limit.

Circle of Interference: Disadvantage from Opposing Mana

When opposing mana types are present in the same aura, they interfere with each other:

Arcane ↔ Fae (Opposition)

If an Arcane caster has Fae mana in their aura:
Disadvantage on arcane spell attack rolls
Spell save DCs reduced by 2
Concentration checks have Disadvantage
If a Fae caster has Arcane mana in their aura:
Disadvantage on fae spell attack rolls
Spell save DCs reduced by 2
Concentration checks have Disadvantage
Solution: Use one system at a time, or wait for mana to dissipate (1 hour per spell level of mana)

Divine ↔ Infernal (Opposition) - Catastrophic Risk

If a Divine caster has Infernal mana in their aura:
Attempting to channel divine mana while infernal mana is present causes a catastrophic incident
Roll on Catastrophic Incident table (see below)
Divine and infernal mana violently clash within the caster's body
If an Infernal caster has Divine mana in their aura:
Attempting to use infernal magic while divine mana is present causes a catastrophic incident
Roll on Catastrophic Incident table
Both mana types attempt to destroy each other violently

Catastrophic Incident Table (when attempting to use opposite mana type): - Roll d20: - 1-5: Both mana types explode violently. Take force damage equal to 2d10 per combined spell level. All spells fail. Gain 2 levels of Exhaustion. - 6-10: Violent backlash. Take force damage equal to 1d10 per combined spell level. Spell fails. Gain 1 level of Exhaustion. - 11-15: Unstable surge. Spell fails and triggers wild magic surge. Take 1d6 force damage per spell level. - 16-20: Barely controlled. Spell fails, but take only 1d4 force damage. No exhaustion, but cannot use either magic type for 1 hour.

Prevention: - Purge opposing mana from aura before using opposite system (requires 1 hour of meditation per spell level of mana) - Use only one system at a time when multiclassing opposite types - Never attempt to channel both opposing types simultaneously

Circle of Interference (One-Way)

Fae → Infernal (Interference)

If an Infernal caster has Fae mana in their aura:
Disadvantage on infernal spell attack rolls
Targets have Advantage on saving throws against infernal spells
Infernal spells have 50% chance of failure (roll d20, 1-10 = failure, resource still expended)

Divine → Fae (Interference)

If a Fae caster has Divine mana in their aura:
Disadvantage on fae spell attack rolls
Targets have Advantage on saving throws against fae spells
Fae spells may have reduced duration (50% of normal)

Infernal → Arcane (Interference)

If an Arcane caster has Infernal mana in their aura:
Disadvantage on arcane spell attack rolls
Arcane spells may trigger wild magic surges
Concentration checks have Disadvantage

Arcane → Divine (Interference)

If a Divine caster has Arcane mana in their aura:
Disadvantage on divine spell attack rolls
Divine spells may be unstable (roll on unstable results table)
May require additional divine mana to stabilize spells

Managing Mana in the Aura

Mana Dissipation: - Mana naturally dissipates from the aura over time - Rate: 1 spell level per hour of rest or light activity - During combat or active spellcasting, mana accumulates faster than it dissipates

Purifying the Aura: - Short Rest: Can attempt to purge one type of mana (chosen type) - Long Rest: All mana types dissipate, aura resets - Ritual Purification: Special rituals can purge specific mana types faster (GM discretion)

Tracking Mana in Aura: - Players should track which mana types are currently in their aura - GMs track the amount (spell levels) of each type - Example: "You have 5 levels of arcane mana and 3 levels of infernal mana in your aura"

Arcane + Other Systems

Arcane mana pool is separate from other systems
Arcane mana can be used to enhance infernal spells (Circle of Enhancement)
Arcane mana interferes with fae magic (Opposition)
Arcane mana can interfere with divine magic (Circle of Interference)

Divine + Other Systems

Divine daily limit is separate from other systems
Divine mana can enhance arcane spells (Circle of Enhancement)
Divine mana interferes with fae magic (Circle of Interference)
WARNING: Divine mana + Infernal mana = Catastrophic incident if both in aura simultaneously

Fae + Other Systems

Fae spell slots are separate from mana pools
Fae mana/spell slots can enhance divine spells (Circle of Enhancement)
Fae mana interferes with arcane magic (Opposition)
Fae mana interferes with infernal magic (Circle of Interference)

Infernal + Other Systems

Infernal tolerance is separate from other limits
Infernal mana can enhance fae spells (Circle of Enhancement)
Arcane mana can enhance infernal spells (Circle of Enhancement)
WARNING: Infernal mana + Divine mana = Catastrophic incident if both in aura simultaneously

General Multiclassing Rules

Each magic system tracks its resources separately
Spell access is per-class - you know spells from each class's spell list based on that class's level
No spell preparation required - all known spells are available to cast
Total character level may affect some limits (GM discretion)
Circle of Interaction applies to mana in the aura - this is critical for multiclass characters
When using enhancement combinations, track both resource types expended
When opposing mana types are in aura, use only one system at a time to avoid catastrophic incidents

Converting Standard Spells to Mana Costs

All spells use the same mana costs regardless of magic system (except Fae, which uses spell slots):

Spell Level	Mana Cost	Upcast Cost
Cantrip	0 (free)	N/A
1st	1	+1 per level
2nd	2	+1 per level
3rd	3	+1 per level
4th	4	+1 per level
5th	5	+1 per level
6th	6	+1 per level
7th	7	+1 per level
8th	8	+1 per level
9th	9	+1 per level

Example: Casting Fireball at 3rd level costs 3 mana. Casting it at 5th level costs 5 mana.

Magic System Interactions with Mana

When magic systems interact, mana costs and limits may be affected:

Opposite Actions (Arcane ↔ Fae, Divine ↔ Infernal)

Mana Costs: Normal for your system
Spell Slot Comparisons: For Arcane vs Fae, compare mana cost to spell slot level
Energy Contests: Higher resource cost (mana or slot level) wins

Circle of Interference

Mana Usage: Interference doesn't affect mana costs
Concentration Checks: Still based on interfering spell level (or mana cost equivalent)

Circle of Enhancement

Combined Mana: When enhancing, use combined mana costs for unstable results table
Divine Enhancement: Divine power can enhance without counting against daily limit (but watch instant limit)
Infernal Enhancement: Infernal enhancement adds to tolerance check—be very careful