It's not a specific mechanic, but a great way to describe this play pattern, and is a much better slang term for describing the archetype than cards leaving the graveyard
The major difference between Pokmon-ex and other types of Pokmon is that when a Pokmon-ex is Knocked Out, two prize cards are taken, as opposed to the standard one
Card Name Mana Cost Type Artifact Rarity Rare rules Text , Sacrifice this artifact: Choose up to seven face-up exiled cards you own
The front faces of each of the 20 modal double-faced cards are all nonland faces, and the back faces are all land faces
You draw X cards and you lose X life, where X is the greatest mana value among cards exiled this way
Thats what this section is here for to cover all of the bases and get you good to play from the second youve finished reading the rules