Familiar Skill List

Is there any way to know if a card is Common, Uncommon or Rare without using it?

Yeah, the little corner color on the cards tell that.

Grey = Common, Yellow = Uncommon, etc etc
(idk the rest lol)

They're also separated in tabs in your monster book if you've already used a few. "C, U, R, L"

Though I don't think their rank effects their drop rate as much as their level does @.@
Mainly seem to be separated in terms of their effects.