I have mixed feelings about this latest card from Dark Ascension... and I'll explain why.
I've been waiting for a 2cc colorless form of mana acceleration and between Warden of the Wall and Altar of the Lost, it looks like my wish is never going to come true.
Warden of the Wall is an interesting take on artifacts which temporarily become artifact creatures. It's a solid 2/3 creature for 3 colorless mana and is going to see as much play as One-Eyed Scarecrow. There really isn't much to complain about. As an uncommon, you can't ask for too much and yet it's very playable in the right format. Good, solid card.
If we want to build a deck around a mana accelerator, first we want to play something else worth accelerating. You probably guessed it by now, but I keep on pushing this casual Gutter Grime deck and Warden of the Wall fits right into this same deck. The warden both accelerates Gutter Grime and also provides a potential body for more slime counters and ooze tokens. Throw in some undying creatures like Strangleroot Geist and take advantage of the warden even more with sacrifice effects from cards like Altar's Reap and you have a deck ready to compete in the casual room.