That's weird the Angel didn't attack/advance though. Ground units not trying to attack flyers? Normal. Flyers with only melee not attacking ground? Odd.
They have to cast a 1000 mana spell "Spell of Return". Just like any spell, you need enough mana to pay for it and it's limited by your spell casting skill. Not sure what the Impossible AI skill level would be at this point in the game, maybe 50 or 100, so 10 to 20 turns? But I would assume they have enough gold to get any mana needed through alchemy. Sometimes if you're a player who gets banished that could be a little harder to scrounge up.
