But Teferi is just the start
In other words, whats the first Pokemon card? Is a different question than whats the first card with a Pokemon on it? If we are going to value a first appearance then honestly the video game is more of a correct answer First physical product to mention/depict Pocket Monsters
Toby, Beastie Befriender A 1/1 Legendary Creature Human Wizard
Any reprint is legal in any format in which it was already legal
Colossus of Sardia Although someone ranked the 90s Shandalar PC game as one of the worst Magic video games (cough, cough), if you played it you likely have fond memories of trying to win with the biggest creature in the game, Colossus of Sardia, before you got your Black Lotus and Time Walks
Even though it costs seven mana, youll never have to worry about losing your late game play since Tyrranax Rex cannot be countered, letting you cast it without worrying about being blown out on your game-winning play