I believe Gilgamesh has an insta-KO ability. That is probably what killed Cecil. As for the rest of the team, it must have been a debuff he slapped on you before he unloaded.his 50% threshold some how 1 shot my fucking 9200 hp 520 or something def Cecil and entire team.
I had Marie with fucking around on the 2nd attempt and had protect up to (no golem was available). Not sure if I was debuffed but what the fuck
On a side note, I encountered a glitched Nimbus today. Started the round with Steal, then I used Chizurus LB to kill the soldier and guarded with everyone else. Nimbus proceeded to KO 2 units. Next round, I guarded with everyone. Again, Nimbus KO'd 2 units. Last round, Chizuru used Hayate and luckily Nimbus did not attack and just ran away. Weird. I would have been pretty mad if I was wiped on the last round because of that.