I'm quite high on this card in theory, and will test. I think asking Spark Harvest (the previous best version of this card) to be an instant is too much. The discard is already substantially easier to pay than sacrificing a creature. Aggro decks will often have a spare land in hand, and they are the same decks that dearly need efficient removal to push through damage, or kill token-producing planeswalkers without falling behind in races. You cannot get more efficient than 1 mana kill any creature OR planeswalker, except tier 1 removal like Snuff Out. Without even considering that the discard is often an upside, I think this could shine in R + B/W token aggro decks - and in reanimator & Daretti shells, it should also fill two roles in one card. Them's my hopes, anyway.