The name is a story-based way of saying cards that stay on the board when played
However, coven feels a bit too familiar to the likes of battalion and pack tactics
Some of these cards fall into more than one group however I think it is more useful to just consider them all as non-mill cards and just group them into high pick high power cards and jank you can easily get if you actually want it
As a companion, it encouraged 80-card deckbuilding in exchange for a free, repeatable blink effect that could reset planeswalkers, reuse ETB creatures, and snowball incremental value
My favorite thing to do with effects like this one is changing the target of a counterspell to Imps Mischief
Each booster pack contains 15 random cards including: 1 Rare or Mythic Rare, 3 Uncommons, 10 Commons, and 1 Basic Land.