How do I teach Doublecast to a Summon?

[MikeL Valentine]

Monster Arena for Catoblepas (Area) and Shinryu (Original).

The Aeon's Soul is found by defeating Begemine your first visit to the Calm Lands, by the Agency. Regardless of the outcome of the battle, you will receive the Aeon's Soul.

Suffice it to say, you won't be getting Doublecast on Shiva any time soon.

Well acually I'm stuck at the Sin encounter, oh how I hate Giga-Gravition
And I can't think of anything else than that

The Arena can be found in the Calm Lands right?