Magic pots are invulnerable to physical AND magical attacks (every kind of damage, therefore) until they receive an elixir. they are immune to Death. The ONLY thing that could actually kill a magic pot without giving it an elixir would be Cait Sith's "Game Over" Limit Break. It ignores status defense and inflicts Death, so it will always kill everything.

By the way, there are only two actions a magic pot can use, and they are Steal (Real Name: Gimme!) and Escape (Real Name: (Report)). "Gimme!" is used with a 25% chance (1/4) as a counter, same with "(Report)", but that only has a 6.25% chance (1/16), but both are only used, if the pot hasn't received an Elixir yet. Magic pots are probably the best enemies to use for the "Super W-Item Trick". And you will always receive a turbo ether, 8000 EXP, 1000 AP and 8500 GIL from Magic Pots.

I hope that's enough of information on magic pots for now...