Jet Medallion, Bolass Citadel, draw spells, tutors, and black cards that lack colorless requirements in their mana costs tend to work best with Krrik, as they help you stretch your mana and card access into ridiculously explosive turns that can win you the game on the spot if your opponents dont have access to any interaction
Capture of Jingzhou Capture of Jingzhou is another sweet reprint
The major downside to this card is if an opponent has lots of creatures in play, like from a token-based deck, you could be stuck with no creatures in play yourself and an army from the token player
Disney and Pixars Toy Story, Alien True Believer Disney and Pixars The Incredibles, Mrs
It can't be blocked by creatures of that color this turn
Landfall also falls into this category of carrying the flavor of characters that protect the environment across their respective games