Unique Status on a NPC

[kvatchcount]

I'm just curious, say I am working on a mod and just had a great idea to add in leveled lists some Unique NPCs to be callbacks to Legends. If, say Tyr or Legate Cassia, was given Unique status, was added and they spawned from a leveled list and subsequently died, would they ever spawn again? Or would they be dead permanently, regardless of the fact they are in the leveled list?

To follow that up, say they spawned, didn't die, and got to go on their merry way? Say like if they spawned in a Civil War prisoner escort encounter. Would they still be able to spawn elsewhere, since these NPCs tend to despawn when the player is some distance away?

Just asking. Because that'll determine if I bestow Unique status to these NPCs.