Upgraded undead?

[Aleolus]

OK, I'm wanting to make some undead that have the equivilent of regeneration. Regeneration requires that the creature have a con score, so just saying they have regen won't work. The thought I have is undead (in this case, Skeletons) who can only be actually killed with energy from the Positive Energy Plane, via a Smite from a good-aligned char (not necessarily Smite Evil), a Turn Undead, or a Cure effect. You can knock them down, drop them, smack them around all you want with normal stuff, but they just keep getting back up till hit with Cure/Smite/Turn. Any ideas?

[BOZ]

fast healing, plus an ability that keeps them from being destroyed when reduced to -10 hp from anything other than the effects you listed?

[dhaga]

Fast healing was my first thought, as well. As BOZ noted, you will also need to create an ability for them to avoid destruction when reduced to -10 hp by means other than Positive Energy. Magic Immunity (excluding Cure spells) and some DR/- could be a good base.