Yorion, Sky Nomad

The oversized deck was always a self-inflicted wound: run more than the minimum and you dilute every draw, so nobody padded a list on purpose. The companion mechanic inverted that logic and made the padding a price. Here the tax is deckbuilding arithmetic, twenty cards past the floor, in exchange for a five-mana body that starts outside the deck and never spends a card to reach the board. That inversion is the whole design: it takes the worst thing you can do to a sixty and reprices it as the cost of admission.

The blink is deliberately mercenary. When it enters, it exiles any number of your other nonland permanents on the spot, then hands them all back at the beginning of the next end step, so every enters-the-battlefield trigger in the deck refires on your terms and a wider-than-usual list turns the restriction into fuel. For a stretch this Bird Serpent functioned as a free extra card in decks with no right to one, which is why the companion rule was eventually rewritten so a chosen companion must be paid for from outside the game (the printed ) before it ever touches your hand. The mana tax was the patch; the effect itself was too clean to keep offering at zero cost. What survives is a 4/5 flier that rewards you for assembling a deck almost nobody would build without a payoff this precise.