This will be absolutely amazing in Lizard decks, but the +1/+1 ability is relevant for any deck that can get creatures in for combat damage
If you can manage it, the card then transforms into World Champion, Celestial Weapon, a powerful equipment
It already mills half of the opponent's library just by casting it, not needing to resolve, has a Ward that makes it hard to eliminate, and has stat line boosts and Annihilator based on the exiled cards in the game
This means it can activate as many times as you want once you have your combo assembled
The strategy is simple: Cast big dragons, and get Atarka on the board to give them double strike
Triskaidekaphile is probably worth a slot since putting lands into your hand at instant speed could creep you up to thirteen cards and the win condition, and other than that, the card draw ability and no maximum hand size are going to be useful