There are some pretty chonky flyers in the decks too, with Brainstealer Dragon being at once a great card for the exile-and-play-opponents-cards archetypes, but also a great fit for reanimator decks that want to steal other players stuff
Casting Endurance for free provides, well, free graveyard hate, which is quite powerful
Avoiding permanents is probably the easiest way to meet the restriction since playing a deck with a bunch of creatures while also ensuring each has an activated ability seems difficult
Ruby cards have an aggressive approach to their playstyle, with abilities and effects that focus on boosting Strength or Willpower for Challenges against other Glimmers or giving the player extra Lore tokens from making Challenges and winning them
You cast the spell while the ability is resolving and still on the stack
Seconds later, I realized I had my card