It looks like Ren is getting better. She will probibly be the first non-Slime 'Goo Mage'. The reason it is hard for anyone besides a Slime to become a Goo Mage is because all the spells for that class can only be cast in the Slime language. That language is really hard to learn witch is why there are no people besides Slimes that become Goo Mages.
Ren baby: [link]
Ren young: [link]