Like being a ghost, being in stasis, being cloned... All sorts of good stuff
Actually, here's a better list of ways to explain how a Pureblood can be up and walking in this day and age:
1)Stasis, though that seems to be everyone's favourite thing nowadays xD
2)Be a ghost
3)Longevity; A healthy Pureblood can actually live for about...300 years I think? Minus external factors. There are also a few cases where the Sith have used alchemy and sorcery to prolong their lives, though this usually comes at a great cost (see: the Emperor during Revan's time, Lord Scourge, and maybe Darth Nyriss; They were all in the book The Old Republic: Revan)
4) A lost colony of Purebloods, either in Wild Space or the Unknown Regions, similar to the Lost Tribe in the Fate of the Jedi series.
5)Being cloned from DNA collected from any old Sith graves known to have Pureblood corpses in it
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