Overall, I think that Commander Masters has a lot to offer, even though I have my own personal nitpicks with some of the card choices and the accessibility of the product
Thats about all I know
The defending player must sacrifice the required number of permanents before declaring blockers
4/4 tokens are a really good payoff, and to sacrifice lands, you can play cards like Harrow, Wasteland, or Crop Rotation
Like most Magic: The Gathering cards, the value of Ajani Unyielding depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Aether Revolt)
Abilities that care about the damage dealt like lifelink and deathtouch will matter, though