I was wondering if you can obtain the eidolons featured in the raids. I'm quite new to the game but I have went for focusing light. My setup contains:

Main Eidolon: Thunderbird
Kamihimes: Undine, Artemis, Hermod, Amon, Hermes, and i forgot the name but light
Soul: Cassiosomething

I was wondering if you were able to obtain the eidolon through gacha or the idea cores that the boss drops.

~~Thanks