Just like with most Nintendo games, Super Smash Bros. Ultimate is compatible with amiibo figures.
By using one of the Super Smash Bros. line of amiibo with Ultimate, players will be able to create a “Figure Player,” NPC characters that players can fight against, train, and level up.
The amiibo Fighter Player will learn as it fights you, so if you were to have it face a competitive player, for example, it could in theory learn moves that only those players could pull off.
It’ll also pick up characteristics from the player. So if you taunt when you KO it, the Figure Player will also taunt when it KOs you. It might stop learning this feature, however, the more it levels up to make room for better mechanics.
In short, the Figure Player will become you and the more it levels up, the better it will become. So the better the player, the better the amiibo Figure Player.
Figure Players are locked to level 70 in Ultimate. Previously, these fighters were limited to level 50 in the Wii U version of Smash Bros. It’s not clear if the Figure Player retains its statistics, levels, and everything it learned from the Wii U version of the game in Ultimate.
It’s also worth noting that using amiibo does not unlock characters early. Even if you own one of the amiibo figures based on a character that could take the longest to unlock, you will still need to unlock them naturally in-game through progression.