Make sure you have a useful primary eidolon in every team, even if you don't use that team. Aim to cover all 6 elements with your primary eidolons so your friend slot in each element isn't wasted.
well, as i said before, i never thought that eido on other team would affect the main

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anyways the event is over in few hours, so no point..
should lvl up da himes for next event