Theres also an OS community focused format that plays with the idea of the Four Horsemen
Building decks around non-legendary creatures was a fun and fresh challenge for me and I'm guessing many of you haven't ever tried it
When you cast the spell with Prowl, you look back at your turn to see if you've done what it says - dealt combat damage with a card that shares a type with the card with Prowl (so, probably a Rogue, but maybe a Dinosaur and in occasional corner cases, Goblin, Faerie, or Sphinx) You don't still have to control the Creature that did combat damage, you just have to have met the condition of dealing combat damage with the correctly-typed Creature
Traveling Chocobo (Borderless Art, Pink Neon Ink) Mythic Rare, 511b Wait, another Chocobo
For both modes, the value of X is determined as the ability resolves
You cannot recur things more than once, so there is a break here, but two copies is just downright good