steelix pokemon card value stage 1 Colorless Iron Tail (100×) Flip a coin until you get tails Steelix Holo - Celestial Storm

There are alternatives to this deck just about any Metal-focused deck, such as Dialga ex and Melmetal, or even just any other meta-viable deck, will probably work

The only real threats to this deck are other Pokemon who can one-shot Mewtwo EX (namely Charizard EX or a Blastoise EX with five Water Energy) or fast attackers like Pikachu EX who will exploit your set-up period to quickly chip away at Mewtwo EXs health

It can start creating tokens at the beginning of your upkeep and hopefully clear the path for your other creatures to make a big attack

The described condition must be true both as your end step begins and as the "to solve" ability tries to resolve