Tested a few things.
- It doesnt have to be an enemy troop. It can be yours.
- It doesnt have to be the last troop remaining.
- Summoned troop comes in with their normal stats.
If this is a bug it effects multiple troops and seems inconsistent.
Vash’Dagon can devour itself and summons after if cursed to negate trait. (tested and confirmed)
Black Beast can NOT devour itself even if last troop. (tested and confirmed)
Sacrificial Priest can sacrifice itself at any point and then has a chance to summon an Aborath. (tested and confirmed)
The Widow Queen can NOT sacrifice herself. If the last troop she instead sacrifices no troop at all. (tested and confirmed)
There may be some specific reason for allowing things like this on some but not others. It just seems inconsistent.