Once you've attacked with it, you can use its [Activate: Main] effect to swap it with an 8-cost Yamato in your trash, giving you even more chances to attack your opponent
This should be cool except none of the other Shinjins have power
For instance, aggressive decks that focus on swarming the field with Monsters may require a higher Monster card ratio, while control-oriented decks might need a more balanced ratio to ensure they can respond to various threats
As a side note, Thought Lash is a blue enchantment from Alliances that has the same powerful, potentially exploitable effect
Summary Mox Sapphire, Vesuvan Doppelganger, & Time Walk are some of the priciest Magic cards, selling for thousands or even millions
At the end of the Battle Phase, if this card attacked: You can banish 1 card on the field