The treasure chest next to a boss stays locked until victory. Then everyone who fought gets their own loot – once per fight.
Other chests are normal loot chests (by tier: simple, medium, rare, treasure) and often hold tech materials of the installed mods.
Traps: pressure plates in halls trigger arrow dispensers.
Spawners burn out after a few dozen mobs.
Riddle: in the catacombs only the right lever setting opens the gate to the boss – lit candles reveal it.