My question is about magic and monster CR. I was building a CR 10 Cleric with capabilities of healing himself and others, but I don't see any rules about calculating CR for a monster that expends his action healing, so I made a guess and ended up with a CR 10 guy. This is the statblock:
- AC 16 (Scale mail)
- HP 188 (25d8+75)
- Speed 30 ft.
- STR 14 (+2) DEX 12 (+1) CON 16 (+3) INT 10 (+0) WIS 18 (+4) CHA 12 (+1)
- Damage resistance Lightning
- Saving throws Wisdom +8, Charisma +5
- Legendary resistance (1/day)
- Magic resistance.
- Spellcasting. 10th Spellcaster, Wisdom (DC 16, to hit +8)
- Cantrips (at will): Light, Sacred Flame, Thaumaturgy
- 1st level (4 slots): False Life, Cure Wounds, Detect Magic, Sanctuary
- 2nd level (3 slots): Hold person, Spirit Weapon, Prayer of Healing
- 3rd level (3 slots): Magic Circle, Spirit Guardians, Dispel Magic
- 4th level (3 slots): Banishment, Guardian of Faith, Freedom of Movement
- 5th level (2 slots): Flame Strike, Mass Cure Wounds
- Multiattack. 2 attacks
- Quarterstaff. Melee weapon attack, +6 to hit, reach 5 ft., one target. Hit: 9 (2d6+2)
- Breath Weapon (Recharge 5-6) 30 ft line, 35 (10d6) Lighting damage, Dex saving throw (DC 15)
Normally she has pre-cast Spirit Guardians, Guardian of Faith and 4th level False Life (21 hp). In combat she casts Flame Strike on the first round, Breath Weapon on the second round, recasts Guardian of Faith (it's probably spent at this point).
That's my idea of her first 3 rounds and there's actually no room for healing. Of course on later rounds she will start to spam heals, specially Prayer of Healing and Mass Cure Wounds will make a difference as long as she is not alone in the encounter.
I can't come up with a simple answer to this. Maybe I should change her rating based on the group she's into, or recalculate the effective hit points of each monster in the encounter to match the Cleric healing. Giving her increased effective hitpoints seems odd to me, because she can't "heal and attack", therefore she's just delaying the inevitable.