As an additional cost to cast Greel's Charm, sacrifice a Swamp.
Choose one – Target player discards a card at random from their hand; or destroy target Human or Elf; or target player loses life equal to the number of permanents you sacrificed this turn.
Instant
Ha! I designed this card in my head for Challenge # 081 today, and accidentally fulfilled Challenge # 082 in the process.
Greel, Mind Raker likes to discard cards at random (as also seen on Flay. That's nice... it's hard to get a good card that only discards 1 card at random... it's never worth the casting cost normally.
Destroying a Human or Elf seemed like a good restrictive creature destruction spell (Originally, I had "Target creature gets -3/-0", like on Greel's Caress, but it was both out of flavor, and not very interesting). And sacrificing equal to permanents sacrificed fit into the "sacrifice a lot of lands" them in a very direct manner. My original plan was to have the last ability be "Return to lands from your graveyard to your hand", but the flavor bugged me. It's strange: That card would feel fine on a
hybrid card, but not as much on a green card or a black card.