Toxic Flask

The flask lobs slowly and drops hard, so anything above you is awkward and anything far away needs a long lead. What it leaves behind is the actual weapon: a patch of gas that sits where it landed and grinds down whatever walks into it. Aim at the floor in front of a crowd rather than at any particular enemy.

The gas will not pass through terrain, so the shape of the room shapes your damage. A flat corridor keeps the clouds packed together. Open air lets them spread thin.

Single tough targets. A cloud is spent each time it damages something, so one boss chews through your gas at the same rate a whole crowd would without the payoff of hitting several things at once. Against an event wave it is excellent. Against a boss with a big health pool it is the wrong pick.

Piling many flasks onto the same spot creates enough overlapping clouds to visibly slow the game down. That is a real ceiling on how hard you can spam it inside a small arena.