Originally Posted by
Slashley
It's not really worth it to use Elixirs on Ragnarok Advents. If you keep playing you'll fairly soon become easily strong enough to do almost all of them with little difficulty.
Your team setup could really use some work, though. You want to be as close to -40% Def and -40% Atk as possible (or more!) with BP, which just isn't a thing with that setup. Getting a Hraes friend means that you can make do with -30% Def. If memory serves, Ixion does a fair amount of damage so Ithaqua most likely can't keep up. I'd say bring BP on Joan and Cybele instead of Ithaqua. Then just kill Ixion before she kills you, which should be doable with -35% Atk and -50% Def (with Hraes friend) and two damage cuts (Joan and Gaia). If it feels dangerous, maybe swap Azazel with good old Zephyrus. Yes, Rs with debuffs can sometimes be far stronger than SSRs without them. Not sure if that's the case for you.
Of course, not using Joan would be the ideal scenario for bringing a B debuff and BP... but based on avatar, I guess that's not on the table.
Anyway, the Demonic Cores are mostly used for the Dragon Eye Shards. They're also used for Final Limit Breaks for Advent weapons (five of them), such as Phoenix Bow in the next Advent. Make sure to get the SSR books from this event to get Gaia to level 80, you'll probably very much need that against Ragnarok Phoenix, unless your Dark team is amazing.