Quote Originally Posted by AznSamsung View Post
use as material or just leave in inventory?
It depends on the usefulness of said Eidolon Skill and whether you think the buff it gives will be important in the future with another team

Also if it had +_ materials, if the summoning skill or the buff it gives might be of use later (say Behemoth-like skill that proves to be mandatory in some events or a boost for an attribute you don't have but might end up getting) then just save it, if you have the attribute covered and the skill is bad or outclassed by another Eidolon's you can sell it or upgrade with it