Given the lack of any new black-bordered cards with this mechanic in the last 16 years, mechanic certainly isnt evergreen and probably won't see consistent printing again
When it enters the battlefield, each creature gets -X/-X until the end of the turn
In other games, however, a resolved Mystic Remora just wins the game as players cast noncreature spells with reckless abandon and the cards drawn by this one-mana enchantment eclipse the tables combined efforts
It feels very similar to a scrapped mechanic from Bloomburrow that batched together all animal creature types, albeit getting around the arguments of what is and isnt an animal by just listing a ton of them individually
Summary Enchanted variants of Disney Lorcana: Shimmering Skies cards hold the most value due to unique art and foil treatment
Return it to the battlefield under its owner's control tapped and attacking at the beginning of that player's next declare attackers step