mew golden pokemon card #1 Shiny Secret GOLD (Celebrations 025/025) Darkness Ablaze Type Mew ex (151 Metal Card)

They returned with more frequency, and finally just became an evergreen mechanic starting with Zendikar Rising

Then, you just use Aetherflux Reservoir to delete as many people as you want for every 50 life you use, you deal 50 damage to that target

Usually, this would be used in a landfall deck to get more land drop triggers, or as a deck thinner to remove a couple of basic lands that you would otherwise draw

Flapple is the most obvious about it, but even Hydrapple seems to have the original apple stuck into its main head's horn showing how much it has grown

You cant get them in packs and they dont show up in Secret Lairs, so the only way to get them (directly) is by being a judge