Because it transforms the enchanted permanent, it doesnt change zones, making this one of the best ways to remove a commander without returning it to the command zone
A standard One Piece deck has 51 cards and 10 DON
That said, this can be easily exploited with flicker cards like Ephemerate, Cloudshift, and Eerie Interlude
$2.99 Mirror March Ravnica Allegiance $0.59 Squee's Revenge Apocalypse $0.49 Memories Returning Final Fantasy $0.35 Tavern Scoundrel Modern Horizons 2 $1.99 Ultima, Origin of Oblivion Final Fantasy $0.79 Jill, Shiva's Dominant Final Fantasy $2.49 Planar Chaos Judgment $3.49 Fiery Gambit (Foil) Mystery Booster/The List $0.49 Firion, Wild Rose Warrior Final Fantasy $0.79 Astrologian's Planisphere Final Fantasy $0.49 From Father to Son Final Fantasy $1.49 Dion, Bahamut's Dominant Final Fantasy 0 results found
Thats already not actually that bad, especially as it being an enchantment means you can potentially bounce it back to your hand and cast it again later on
There's only one Master Emerald, and it's kept considerably more secret