Ikorias Companion Cycle Umori, the Collector Gyruda, Doom of Depths Zirda, the Dawnwaker Keruga, the Macrosage Lutri, the Spellchaser Obosh, the Preypiercer Kaheera, the Orphanguard Yorion, Sky Nomad Jegantha, the Wellspring Lurrus of the Dream-Den Ten companions from Ikoria , one for each color pair, all hybrid-mana cards to work best in Limited
There are Voltron synergies, tokens, lifegain, and more
It's one of the most impactful moments in the game, and I was still surprised how much it got to me while playing Final Fantasy 7 Rebirth , despite having known for years it was going to happen
This creates a value loop where you get your ETB triggers twice, once for the original and once for the token, all for a massive discount in mana
All of these cards can easily go infinite or just massive