Amiibos are toy figurines that can be placed on the gamepad to bring a character into the game utilizing NFC technology. Chips inside the figures save customizable data so that a player's character will be the same whether they're playing on their own system or at a friend's house.
Nintendo's E3 2014 presentations seem to indicate that Amiibos that are brought into the game will not actually be controlled by the player; rather the player can watch them fight, fight against them, or fight alongside them. How the character behaves when brought into the game will be determined by how the player has customized them and how they have leveled up.
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