Duelists can only have up to 3 copies in total of each card across all Decks
I didnt wanna tag them here because everyone else probably might, but you can search for it
Umaro, Raging Yeti* Straight to you from the World of Ruin in the Revival Trance Commander Deck, Umaro is a beast of a design as a 6/6 for 6 with trample who will either pump your board, shoot something, or wheel you each turn at random
Seat of the Synod is the king of the colored lands, because blue is the color that works best with artifacts, and Vault of Whispers is second because of Disciple of the Vault, but all of them have joined the fun at one point or another
Even Cat decks may well be eying up Scythecat Cub to gain value from otherwise wasted land draws
It continually gets worse as the Zarc arc continues as the Lancers and their allies, made up of the various dimension's strongest duelist failing to both defeat Zarc and make Yuya react from inside of Zarc