If you right click really fast on the monster, you can even triple cast spells in one turn. This doesnt work when a monster is right in front of you but if you have no adjacent monsters, you can do it. Its ridiculously powerful and should be fixed. My 40 something spell power mage was killing EVERYTHING with a double cast of the cyclone skill from viking tree. With vamp magic and 7 mp regen, it was pretty much a cakewalk. Then i got overcomfident and tried to kill all of Brax's goons on the previous level which didnt end too well lol.
I'd like to see the build that could actually kill all the Dread Collectors on a level. It'd have to have massive group damage capabilities (unlimited squid bolts?), since your enemies multiply. Presumably you'd go around closing all the doors on the level before getting started, to limit their expansion capabilities.
Using fire runes, I was able to kill them all in the spot around the stairs, but i had no chance of actually advancing to Brax to kill him (all 3 of him lol). I died cus i got cornered onto the stairs, unable to go down or move anywhere lol. I had tons of potions of all kinds including invisibility(which i forgot to use) and he critted me for like 35 damage.. RIP