It has to be the negation blast thing. My last attempt was extremely fast in getting to the brain. I killed the Emperor then ignored everything else, just focusing on getting my party into the portal. But it was a complete party wipe on the Brain's second round.

Main character got there first, and hit with 3 attacks (hasted), Shadowheart got there next and just healed. Lae'zel got in that same round and Got 3-4 ranged attacks. Gale was still a ways out.

Next turn, main got a SA, regular attack, and offhand attack. Shadowheart missed. Lae'zel got 6 melee attacks. Brain was at 58hp.

Then we were all dead. It was that fast.