I would be the mist spirit because it would be fun. I would find a lamp and pretend to be a genie whenever someone walked by.
I'm sure I could be an even better charades player as well. I'd hold up 11 fingers (Hey, I'm made of mist) and Vin would say 'Okay, Eleven words' and then I'd nod my head. And then I'd point to an invisible watch on my arm and she'd say 'An event' and I'd nod again. Then I'd hold up one finger and she'd say 'First word' followed by my nod. Then I'd wave my arms back and forth over one another, she'd say 'Safe' and I'd shake my head no and then she'd say 'No' and I'd start twirling my finger signifying that she needed to keep guessing and then eventually she'd say 'Don't' and I'd put my finger on my nose. Then I'd hold up 11 fingers and then point at the well. Naturally she'd say 'Well' and I'd point to my nose again. Then I'd just twirl both hands until she said 'Don't let the evil force of Ruin out of the well.'
If I could talk, I would say 'Get ready to laugh, get ready to laugh' and then I'd make my head appear out of the back of someones pants and say "Gee, must’ ve taken a wrong turn at Albuquerque!".