Ok so first off when i say unkillable i mean "seamingly unkillable". I have an idea for a campaign setting using old characters from a ridiculously high level gestalt 3.5 game i was running, and basically i want to make those characters into the bad guys of the campaign.
We have a ghost bard/sorcerer, human dread necromancer/no idea what to gestalt, a succubus magus/same issue, a vampire rogue/something(archer), and a drow shadowdancer.
Here is what i need help with. The succubus was originally a paladin of slaughter/hexblade. With that she had a nightmare cauchemar mount. What classes and feats would give me this mount legit?