pokemon prime cards Grass Ability Forest Breath Once during your turn (before your attack) Mew (Prime) - Holofoil Triumphant

Ephemerate is one of those cards, which can be either non-existing or almost dominate the format , so I currently see it in between being really good in 4c Elementals/Omnath and Esper Reanimator

If you pick up a couple of UR/UB duals and a World Map, you could use those to splash the powerful Shantotto, Tactician Magician, which plays incredibly well with those spells

So unless there is some pattern where similar cards appear to be rarer or more common, or the sample size is a lot larger, brute force wont deliver definitive answers (though it is still interesting of course)

Once you get to attack with it, it enables you to leverage your yard as a second hand