Backfire

Skill details

Full: For 10 seconds, whenever target foe casts a spell, that foe takes 35...119 damage.

Concise: (10 seconds.) Target foe takes 35...119 damage whenever it casts a spell.

Domination Magic	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21
Damage	35	42	49	56	63	70	77	84	91	98	105	112	119	126	133	140	147	154	161	168	175	182

Acquisition[]

The damage taken from casting a spell is received when that spell finishes casting but before the spell takes effect.
When Backfire's damage would be lethal, AI casters will often cancel a spell just before it would finish casting. Since the spell is immediately available they may cast it again, then cancel again. High cost spells can cause a drastic drop in energy.
The game's AI will only use this skill on targets wielding caster weapons. Switching to a melee weapon can be useful to avoid being targeted by it.