Turn Spellcaster Normal

I think you have to ask one of the sages to perform a rite.

builtin game cheats can do the trick.

Edits taken from Carls Sims4 guides web site.

Cheat Code Result

traits.equip_trait trait_Occult_WitchOccult Change your Sim into a Spellcaster

traits.remove_trait trait_Occult_WitchOccult Change your Spellcaster Sim back into a normal Sim

traits.Equip_Trait Trait_OccultMermaid to change human gallery sim into a mermaid.

traits.remove_trait. trait_occultmermaid to change Mersim to human

Enter cheat before entering cas

PS, these May needs caps rather than lowercase. Experiment with it.

Hope this helps

@Mariefoxprice83 @shorty943p Thanks, I'll ask one of the sages and if that doesn't work, resort to a cheat :)