Lore Hot take: Galio should have been from the Blessed Isles.
Ancient statue made to protect the Isles.
Still make him petricite, but the black mist didn't work like normal magic.. It wasn't absorbed like normal magic. Like negative-magic.
It deactivates Galio, who lays dormant for ages. And then lore stuff happens and stuff I haven't thought about which awakens him to a world where his beautiful society is darkness and death.
Thoughts?