DM: at this point you are basically Consumed by the mimic’s amorphous form. You have three rounds before you start to suffocate.
Fighter: I want to make an athletics check to brute force my way out of it.
DM: Okay roll.
DM: You manage to thrash around a bit and get a part of your body outside the blob. That part is… *Rolls* your ass. Andrus (the npc) is going to grope you and try to pull you out. Make a con save.
Fighter: Umm… 4.
DM: You’re aroused. It’s probably the asphyxiation getting to you.