He doesn't have to. 100 fire damage a second for 10 seconds. Shot out from his sword.
Its how I killed Vivec.
LMAO, game mechanics.
Took some effort, preparation and a good bit of luck. Just for fun I usually make a dwarven shield that spat out target shock, 5pts for 75 casts. Call it the gattling, never does much but its fun to look at.