The creatures which untap multiple lands provide too much opportunity to go crazy since theyre so easily re-used, so Palinchron, Peregrine Drake, and Great Whale are right out
Single-digit temperatures
The Prydwen, Steel Flagship Send In The Troops The Prydwen feels like a Parhelion II that has been tweaked to be more viable a commander
Also the artist of the art I'm not sure of because I got that picture a while back when I first started making cards and I was doing an Android styled set
Yes, sure, it can go into any green deck and start putting counters on things, but to get the real synergies with this going, you need to be in a dedicated +1/+1 Counters deck
The bar of playability is much lower for a card that can work in a tribal deck (see: Cursecatcher in Modern and Mist-Cloak Herald in Standard), so the floor for Mistcaller is that it ends up a good option for Merfolk tribal decks