Guts isnt a particularly popular card outside of Vintage Cube, and its sudden appearance has made some players speculate that MTG Arenas ultimate goal is to add Vintage Cube to the client
When you are designing a new mechanic for your set (or for your game in a general game-design sense), the first question you ask yourself is, "What is it?" You have to define the space it fills and figure out what role it plays in your design
The rares have seen some play as well, so they are pushed
Ajani Steadfast can give a creature +1/+1, first strike, vigilance, and lifelink at a +1 loyalty activation
// Black Chocobo Creature Bird 2/2 When this permanent transforms into Black Chocobo, search your library for a land card, put it onto the battlefield tapped, then shuffle
These pice de rsistancedecks dont need to break the bank, though