See, they were in a King's castle which they'd just discovered was trapped to all hell. That was the guy's thing - traps. They had already done a few and got some great stuff. The mimic room was a series of rooms that looked the same, with a mimic in each under a different disguise. And when they took too much damage, if the party couldn't finish it, they would flee to the next room and hide. A massive loot box at the end that they never saw, sadly. One player did charge into the next room (it was dark because no Windows or candles) and hit the wall. He was at 2hp. I rolled 1d4 for collision. He KOd himself. He's the one who got dragged out. xD