Acererak has more than one phylactery, spread across dimensions.
It shouldn't be possible, that should should snap the connection, but he found a way. It's said in the 4E adventure that Acererak wasn't seen for a thousand years after Return. In the morally right but not Golden Ending of Return, freeing the souls should only limit the lich for a few centuries. The Canon ending was that the lich was destroyed but he still had an out. It took longer to regenerate, and it went to other dimensions to do so; but it was still Staying Alive.- Unlike Voldemort, Acererak always keeps his phylacteries safe; and if brought down to one left; just leaves a dimension to recover instead of gambling it all for revenge.
- Possibly Confirmed. At the end of 'Tomb of Annihilation'', there is no phylactery to find because he keeps it on a different plane. It even says if you win that he'll likely wait elsewhere until old age kills your characters.
