Orcish Bowmasters is a great card for this deck (or any deck with black in the color identity), and can potentially double your army's growth rate while whittling down your opponents
Luvdisc from Crown Zenith, Jirachi from Paradox Rift, and the Piplup from Legendary Treasures are all great starting points
Rather than playing something thats mediocre against two and a half things, you can play a card thats great against a single archetype and not occupying a slot in your library against other things
There is a possibility of sudden deletion
Anyone familiar with the antics of Clifford the Big Red Dog will immediately understand the idea behind Mowu: hes a Dog, and he gets very big, very fast
Thats a real shame given how many cool control cards there are here, like the incredibly potent new Teferi, Who Slows the Sunset, who is sure to be a control favourite in any format theyre legal in