When do you get lucifrom's curse or some other debuff that increases your spell cost it just bug your rune system, what I did on those core hounds was just spreading debuffs and spamming blood boil, it just bugged because I could use blood boil forever, like it had no cost... those 2 death runes in the middle (2 frost) just stood there, have not recieved any normal rune cooldown, so I could just spam blood boil and 1 rune spells without any cost.
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