Goblin Lore is an example of this
Flash is great in duels since you can flash out when you are attacked to block, or kill an attacker with a Ravenous Chupacabra or Eternal Witness a key instant thing like Swords to Plowshares or Counterspell to cast it instantly in response to something
The original Infernal Spawn of Evil was born out of artist Ron Spencer submitting a sketch of a small rat drinking hot cocoa as the art for a card that was supposed to be a demonic horror
The very first time I got to draft the set, I managed to pull together a very strong version of the BG Elves archetype with Miara and Kamahl, Heart of Krosa as the commanders
Warp is a mechanic designed to work around all aspects of EOE, like casting two spells a turn, stationing spacecrafts, or triggering void
It comes down early and grows with cards that can be sacrificed, most notably Treasure, but fetch lands also do it