Many S/T cards today have effects that trigger off of being destroyed by card effects (True King and Abyss Actor, for example)
Essentially lots of players think that the 2021 expansion has artificially low pull rates for the rare cards and, while there's never been any real slam-dunk proof of this, the idea has real traction among Pokmon TCG fans
The Haunt of Hightower The Haunt of Hightower feeds on discard and mill alike
There were four warriors-matter cards in Khans of Tarkir (all in WB) and four Gates-matter cards in Guilds of Ravnica (one blue, one Boros, and two artifacts, which makes sense considering its the play-all-the-colors archetype)
Both Comfey and Colresss Experiment LOR allow you to draw cards and put cards into your Lost Zone
Camp: Violet Poison Magician appears to be one, possibly referencing Yuri's Agent Peacock tendencies