Ultima skill when?

[TankHunter678]

This would be true except that

we've fought a creature that very likely is where Ultima came from and Ultima itself as used by Ultima Weapon was likely an imitation of the Ultima used by the High Seraph. A being considered to be a living primal. So it makes sense that Ultima as a "primal" can impart its secrets at least onto Summoner, and if Ultima Weapon could have an artificial Ultima created, then the players could probably copy a real Ultima now.

However...

we do not know if Ultima was an actual primal or an entity similar to Midgarsormr/Omega as it is talked about as it was not of this world and descended upon the world, this would make it unsummonable and we already killed it.