mtg all merfolk cards The 46 Best in Magic Ranked Mint / near mint condition trading card Mindspring Merfolk | Promotional |

This makes it a powerful card, but not something that every deck will be able to play

You can tap any three untapped artifacts and/or creatures you control, including Warden of the Inner Sky itself and other creatures you haven't controlled continuously since the beginning of your most recent turn, to pay the cost of Warden of the Inner Sky's activated ability

Can you actually play them at a tournament

In the official reveal tweet, its mentioned that today is Zells in-universe birthday

Grand Arbiter AugustinIV The problem that Grand Arbiter has is that you are both playing a tempo-you-can't-do-things build while the player is not even bothering to end the game quickly