So my guild was running 10 man Ulduar last night and we ran into a little trouble. Everything was going well, we downed leviathan, razorscale, xt, and kologarn without wiping once. Then we got to ignis... Normally this is just another boss we kill easily, might take a few attempts if there's new people but we've killed him every week this far. However, we ran into something entirely unforseen. 4 of our dps died pretty fast, which was a surprise and no one could quite figure out what killed them. We didn't feel like wiping though so the rest of us continued to fight him. With only 1 dps alive, it took us a long time. 15 minutes into the fight, he was at 600000 hp, he started one shotting people. Looking at the combat log, he had hit our tank for roughly 150000 total damage.
My question is, where did this enrage come from? Everything I've read suggests that ignis doesn't have an enrage.