They must all be the same color or design, size, and thickness
With its emphasis on creature types and quirky but powerful mechanics, many of the best cards from that blocks various sets slot nicely into modern Commander decks
Y'shtola has vigilance, which means she may attack without tapping
Tap this card: You and target opponent each draw a card
You can get a fleet of small utility creatures like Orcish Bowmasters, Honest Rutstein, and Priest of Fell Rites or go big with creatures like Archon of Cruelty and Serra's Emissary
If Rootwater Shaman were our commander, I'd absolutely consider it, but I can't have a bunch of sorcery speed cards that are bad unless I draw and keep alive an obscure, fragile Merfolk from 1996