I don’t blame Lalali-Puy for not wanting to go Avanion; the XP-requirements are insane!!! I’ve never known anyone to make it to 20th-level, starting at 3rd in Dark Sun, despite having Dragon-Kings since '92.
I see no problem with using animal-life to create plant-life. Life-mana is life-mana. Also, there’s fungus, which, can thrive underground on Athas, and is probably the dominate life there.