Bloodthirsty Adversary is such an interesting card. If you start with the floor of a 2/2 haste for two, that’s already a totally reasonable card in an aggressive deck. Robber of the Rich is rotating out, but that card had reach and also the ability to play a card from the opponent’s deck. That certainly came up sometimes, but it wasn’t terribly common.
The big upside for Bloodthirsty Adversary is that you can pay three mana as many times as you want when it enters the battlefield, and for each time, you can cast a card with cost three or less from your graveyard. This is an extremely powerful effect. At just five mana, you can use the card to cast a copy of a card like Frost Bite, Magic Missile, Burning Hands, Roil Eruption, or Moonrager’s Slash. A five-mana 3/3 haste that does three damage to any target when it ETB is pretty strong, particularly when it can also simply be played as a two-mana 2/2 haste.
I think the ultimate upside of being an eight mana card is extremely relevant as well, and maybe overlooked. Sometimes for a deck like a mono-red deck, you can be against a slow deck that gains control of the board, and get your opponent to like eight or nine life. If the game goes really long, it’s definitely realistic to draw a burn spell and use this to cast two more from your graveyard.
I think this whole cycle looks like it’ll see play and be pretty strong, but I’d say this is the one I’m most excited for.