Am sure the AI (and player if the situation ever presents itself) can surrender, in which case all their towns / units are destroyed / erased, and you receive their Sovereign as a unit (to be your champion), but he/she will be found at the location he was when surrender took place (with no troops on him / her, but with all buffs, equipped items etc).
That because I had Porcupinee (ops meant Procipinee
) surrender to me in a previous game and that's what happened. Interesting fact is that if the surrendering enemy Sovereign, had cast on them buffs which can only exist on only 1 unit at a time, like Tireless March, you end up with duplicates if you already had that spell cast on one of your own heroes. Not sure if is bug or just a bonus of surrender 
BTW MadDjinn, great LP's, looking forward to episode 3 of Bandit Queen, and as a request if you could possible make one with the Kingdom you love so much: Kingdom of Tarth, Lady Irane! Sovereign path: Assassin. Looking forward to it 