Disclaimer: I will not focus on Art or grammar, unless the latter would make the deck too difficult to understand.
Maverick time then!
It took me a bit to go over the cards and fully grasp the gameplay loop involved with the deck. But after grokking it (I hope), I have to say I like it? Assuming these cards only attack once each, even if they have been to the hand. There's a nice ramping threat level to one of these coming up, hitting something, and then going to The Hand to be replaced by a {Normal} (Then {Weak}) Warrior on the Field. And the more these are played, the more that loop keeps growing, becoming really scary if those {Teamwork} Tokens ramp up too. It's honestly really clever.
For points I'm less sure about, I have to admit hook-wise that the idea of the Grand Melee happening every 25 years got a few blinks from me. Is there a specific reason in your campaign setting it needs to be that long - about a third of a normal human's lifespan? Even Real Life Olympics have just 4-year gap between them. Mechanically, I wonder if some kind of Simple Card Move to help with the gimmick directly is not uncalled for? Difficult to say without testing this in practice, though.
Good job!