Ancient Cellarspawn Im probably being hyperbolic putting Ancient Cellarspawn at number 1, but Im floored by this card, and none of that has anything to do with the cost reduction ability
Narrowness of Effect We tend not to do too narrow of effects at mythic rare for the same reason that we watch comprehension complexity: it's important for the mythic rares to be as exciting to players as possible (within the confines of what's good for the game)
Binders are still the norm for the common collector, graded cards are kinda niche, especially in other countries than the United States where grading is less known
Claim Jumper doesn't specific 'basic land,' so you can fetch up dual lands, triomes, or any non-basic that has the plains subtype
Grading the card will cost money, so you should only do this when the card seems to be worth a lot