Locations might prevent characters from being challenged, bolster their stats, and way more besides
Top 41 50 Mono Blue Commanders in MTG Magic: the Gathering Numbers 41 through 50 of the top 100 include these commanders: God-Eternal Kefnet : Kefnet: stands out by turning the inherent blue strength of card draw into proactive gameplay
Prototype MTG Mechanic The Brothers' War features prototype cards, which have a mechanic that represents an artificer's work in different stages of development
You can create pretty consistent scenarios where you play a room card and unlock the other door: Victor, Valgavoth's Seneschal lets you surveil 2 while your opponents discard a card
Repeatable sacrificing is pretty rare, and can force a sort of soft lock on people, so I think this is definitely potentially playable, also in angel tribal its pretty good
BIG cards from Collector Boosters could have a special Booster Fun treatment: the vault frame treatment