Originally Posted by
Gludateton
For Apocalypse event SSR spear is priority (after half elixirs, half elixirs are always top priority), if you have enough materials to get 4 copies and final limit break it that is. After that it depends, if you don't have enough eidolons, get Apocalypse herself. SSR sword is not bad also.
Only effect from main eidolon applies to party, rest are there just for stats and for summoning during battles and sometimes for effect of main eidolon (for example Anubis, Managarm, Horus or Pazuzu).
Berith is top tier dark Kamihime, Aether and Nephthys are both pretty good too. I'd save jewels though, even more so if you main thunder.