Ideally, they take a cheap original card that shares as many characteristics as possible with the card that should be proxied
Instead of that function triggered by attacking or entering the battlefield, Teshar's trigger happens whenever you cast a historic spell, which means his power level can be lower (if you have no historic spells to cast) or higher (if you can cast a lot of historic spells) each turn compared to the other two options
He is a deeply faithful member of the Great Victory, an order that worships challenge and perseverance
I only had space to cover a third of the current legal companion pool today, so perhaps in future we can revisit the topic and cover some of the cool options for playing around the others
You may put that card on the bottom of that player's library." We liked that this new first ability had built-in synergy with the Brainstorm ability
For instance, if a card is limited to only 100 copies or less, it will be vastly more valuable than a card with an abundant print run
