Channel - , Discard Takenuma, Abandoned Mire: Mill three cards then return a creature or planeswalker card from your graveyard to your hand. This ability costs less to activate for each legendary creature you control.
An untapped black land that can dig and recur creatures or planeswalkers at instant speed. Grapple with the Past is valued at 2 mana and saw standard play, and while both cards are very different on paper, both are used to provide mana early or gas in the late game. Being able to grab planeswalkers is big game for both control and midrange decks, and while I doubt the uncountable nature of this card will be particularly relevant, the fact that it plays well with land synergies like Wrenn and Six and Life from the Loam can be very relevant in-game, in addition to being targetable with land-based dig like Once Upon a Time and Wrenn and Seven. I can't imagine the legendary mana-discount clause being particularly relevant with any sort of consistency, but it doesn't hurt that this may cost as little as on choice occasions.