Wow, I thought that this idea would be a total cliche, but apparently I was quite mistaken. I think that it would have it's own class levels and CHA, WIS, and INT. The INT would allow it to have class levels, and it would make sense that it would apply those levels to the host creature. However it would definatley use the host's STR, CON, and DEX. As for sunder and desintegrate, Adamantine much? Perhaps some magical warding?