Voidsent maturity

[TheMightyMollusk]

I think they established unless you're killing them in their home realm, the stronger voidsent don't truly die as they manifest in other worlds by sending their souls across the rift to possess something as a temporary vessel and will simply be banished back to void if their physical form is destroyed (Assuming their soul isn't sealed away somehow instead).

You're thinking of the Burning Legion from Warcraft. Dead voidsent are just dead (assuming they're not just playing possum, like Diabolos in the Lost City of Amdapor). The only known exception is the Cloud of Darkness, who can't be permanently killed because she IS the Void.