I, like most, have probably failed more then once by casting
avenging angel on angelic guard.
Also discovered another thing today. Not really a mistake, more of a bug.
My ancient phoenix died at the same square where enemy heros dead phoenix was. When he used rebirth it was my phoenix that got revived.
Then it died again and so he rebirthed mine again! Never moved it cuz I wanted to keep his phoenix "dead".
Ended up having this phoenix die 5 times!