Board Thread:General Discussion/@comment-26340222-20160312083026/@comment-25536775-20160313212039

Wouldn't have been the first time, not even in Once, where someone pretends to be a God, but is in fact just another generic magic user.

To me, the Trident allowed Ursula to use her mermaid power as magic. Instead of just having a compelling singing voice (Which was taken from her) she could wield spells, but maintained the same power level.