Imprint was a mechanic from Mirrodin block (and later reprinted in Scars of Mirrodin block) where the player had to exile a card when casting the spell (the exiled card came from different places), which then was used as a marker to determine something about the spell
Add in first strike and trample, and its both a tutor and threat rolled into one
The best predictor is EDH use, especially since these are all legendary and likely to be Commanders for decks
Whenever one or more creatures you control with base power 0 deal combat damage to a player, create a 0/0 green and blue Fractal creature token
Toughness-matters decks tend to be stuffed with Walls and creatures with defender, the kinds of hidden gems youd usually find gathering dust at the bottom of game store bargain bins
Isshin, Two Heavens as One Isshin, Two Heavens as One is hands down the best samurai you can run in the command zone