For formats that care about colour identities like Commander and Brawl, be sure both sides fit entirely within your Commander's identity, otherwise, they are not legal
Casting Cost: Card Text: At the beginning of combat on your turn, choose a kind of counter at random that Crystalline Giant doesn't have on it from among flying, first strike, deathtouch, hexproof, lifelink, menace, reach, trample, vigilance, and +1/+1
Smash hard, trigger Enrage, and melt the table
(The early Plague Rat decks preceded the little only four in a deck rule.) So Brian let the card break the rule
Thassa, Deep-Dwelling A source of blink thats both difficult to interact with and that can start to turn the tide in grindy matchups with the expensive tap down ability, Thassa, Deep-Dwelling is a possible commander, but it really occupies that niche of a must-play card in any blink deck you build in Commander
This is Part II of our third trip to Innistrad