Sundering stuff established in the Q&A

[KageTokage]

The Allagans did also have means of transferring memories, so it's possible they just stored away Xande's memories for science.

Actual resurrection via yanking someone's soul out of the Lifestream has no documented successes anywhere in the established lore.

[Jandor]

The Allagans did also have means of transferring memories, so it's possible they just stored away Xande's memories for science.

Actual resurrection via yanking someone's soul out of the Lifestream has no documented successes anywhere in the established lore.

Presumably the resurrected Xande had a different soul, but there have been a couple instances of pulling souls from the Lifestream.

W'nahja was pulled back from the lifestream during the level 50 Alchemist quest, though that didn't last very long. I suppose it's possible the Allagans/Amon could have found a way to make it stick somehow.

There was also Emet and Hythlo at the end of Endwalker. Maybe they were somewhere else, but I certainly got the impression they were in the lifestream before the grand finale.