Elves of Deep Shadow and Deathrite Shaman help fix your mana with black and Priest of Titania can skyrocket your available green mana
Ornery Tumblewagg is another in a long line of +1/+1 counter every turn cards like Luminarch Aspirant, Fight Rigging, and Siege Veteran
Already we've seen new versions of the Eldrazi titans, reprints of the valuable MTG Fetch Lands, and plenty more
Although the tokens enter attacking, they were never declared as attackers
From that point forward, R&D included the occasional coin-flip card, but other than being on red cards and artifacts, there wasn't much mechanically tying the coin-flip cards together
I am happy with the design of Grim Guardian because I believe it serves this role well