A Sage Job Class... (Minor Spoiler)

[Zohar_Lahar]

I'm pretty sure that spell was Breakga, which is also used by the Doga Clones in Syrcus Tower.

[SnowVix]

If he does... then that will occur off camera.

I would be more inclined to believe he learns it in Garlemald. Based off the announcements, we're already going to the moon, Thavinair, and Garlemald. Also I could be wrong here, but didn't Sharlyan disappear? I feel like I remember reading about that in the Eureka questline. But I it's been ages and I didn't really care much for what was going on there at the time.

that was only Baldesion and the Isle of Val that disappeared like that

[Ceasaria]

Maybe I am wrong, but didn't Louisoix was called a Sage ?
And it's the grandpa of the twins, so maybe Alphinaud could learn the job from texts/books written by Louisoix he will find in Sharlayan.