If you don't control both Fang and Vanille at that time, the ability won't resolve, you won't have the opportunity to pay , and none of the ability's other effects will happen
That would be quite good if the Terastodon was at all good as a threat on his own but lacking any evasion or resilience he is just awful
Legend Dragon dor
Meanwhile Veteran Beastrider lets you dictate the pace of the game, excelling on both offense and defense
Card Name Mana Cost Type Creature Human Wizard Rarity Rare rules Text , Sacrifice this creature: Counter target noncreature spell unless its controller pays .Disturb (You may cast this card from your graveyard transformed for its disturb cost.) P/T Number 61 Language English Legal Formats Brawl, Commander, Competitive Brawl, Historic, Legacy, Modern, Pioneer, Timeless, Vintage Not Legal Formats Alchemy, Pauper, Standard Rulings (9/24/2021) Disturb is found only on the front faces of some double-faced cards
While Im not completely sold on mixing IPs in my Commander decks just for the sake of including the best cards, I am easily sold on wonky, sub-optimal builds with a stupid theme