Mid Range Mother
This is my version of the Mother of all Yaks deck. I find this to be quite optimal.
It's still early days though, and would love to chat shop on Yak deck with anyone so take it to the comments, or message me on the discord or something.
Given the game plan revolves around using the blue yak to buff the other yaks up, taking over one side of the map and snowballing some yaks. I felt a mixture of buffs and board control, as well as a little mobility were the best options for filling out the deck beyond yak synergy.
As your yaks die they can power up the mother, so she can help you make a come back, hold back damage and things like that, as well as being used offensively. I like to think of Mother as a failsafe though. The yaks will usually win you game, while your board control options tie things up and clear threats. If your Yaks get destroyed though you can play mother while you regroup and attack again. (hopefully you have saved a sapphire yak if the other 2 died, as this guy is the lynch pin in this deck)
The long horn yak passes it's buff on to the next card drawn after he dies as well, so they are prime targets for farmers from the opponents well.
You have to learn which guy is best to buff up. sometimes buffing longhorn is best if you want to trade it in and power up mother, as it passes the buff on to the next creature drawn, sometimes you will want to play a topaz in a way so it picks up and then goes face, gaining the buff from multiple sapphire's at once. Then adding further buffs, and even having the buff transferred from the long horn can be devastating. If you have a big buff passed on then gain another big buff you will have way more than OTK on it.
Sometimes you will buff green, while using the add to deflect any incoming damage and allowing you to take another buff before trading.
The deck has potential, and certainly has a ton of synergy. There are probably better decks out there for ladder climbing, but if fun's your game I'd recommend this as you can still win with it.