Chaos, Chaos!

Hewwo! I'm making a multi-room trap that includes a random-effect-generator to make things more interesting (roll a d12 at the top of the round, affect the players/battlefield in some way), but I need some help coming up with effects. I'm not really looking for straight damage, more modifiers.

Plz help!

Tiny room/large guests - Everyone increases by 1 size. It’s probably gonna work best in an area with tight corridors and wider rooms for the squeeze rules to come into play.