Noob question: Are the Demonic Cores from Ragnarok only used for the Dragon Eye Shards?

This is the first time I've attempted Ragnarok in Advent Battles, and since it didn't cost anything and Wind is by far my strongest team, I thought I'd give it a go. Yesterday I wiped out with a single character's burst worth of HP left on Ixion, so I used an Elixer. Today, I managed to get a Hraesvelgr friend and managed a win with no Elixer, but it was a bit harrowing when Ithaqua was the first to drop. Hastur was next, but by that point it was already in the bag.

Joan20, Gaia(Awakened)70, Hastur80 in the front; Azazel80, Ithaqua70 in the back; with Cronos70, Cybele70 on standby.

Anyhoo, I wanted to know if there's anything else the Demonic Cores are used for before I start using them for Dragon Eye Shards.