Your choice depends on how many cards you have, how often you play, and how much you want to protect your collection
Shirei is worded in a way that lets you loop Creatures on your opponents' turns too, so with a free sacrifice outlet you can get triggers from cards like Bone Shredder, Dusk Legion Zealot, or Abyssal Gatekeeper
It already has a good head start since it takes the initiative when it enters the battlefield, and the first room of The Undercity lets you search for a basic land, guaranteeing youll have a land drop when you need it
Mardu Vehicles runs Unlicensed Disintegration, which not only destroys a creature, but also goes to the face for 3 if you control an artifact
MTGs toxic set One thing youll notice when you open your first packs in MTG Arena, which is honestly among the best PC games , is that a lot of the cards in green, black and white have the Toxic keyword ability