The big one was its complete lack of mobility abilities or ranged attacks, so a party with overland flight could attack it pretty much with impunity. Iirc that was most commonly paired with shrinking a bunch of boulders, carrying them up with you, then dropping them right as the shrinking spell expired. This is all from memory 15 years ago though so details could be a bit sketchy.

By default yes, but you can set it to work for anyone on your friends list.