Today brought the final Nintendo Direct dedicated to Nintendo's next major release, Super Smash Bros. Ultimate, a crossover fighting game that brings characters from several franchises together in a single adventure. With Masahiro Sakurai, the person responsible for the series, presenting, we received the following confirmations:

Ken Joins the Fight
Ken, from the Street Fighter series, joins the game's roster as an echo fighter of Ryu, meaning the new character is “based” on Ryu. However, he has several distinguishing elements in his movements and attacks, including a spiraling attack and a focus attack, while the character's kicks change depending on the commands the player enters. The shape of Ken's Hadouken is also different, and he is faster than Ryu.

Incineroar, from Pokémon
Another character eagerly anticipated by many fans was also revealed: Incineroar, an advanced evolution of Litten from the seventh generation of Pokémon. Incineroar's moves are heavily inspired by professional wrestlers. They include a slash using its claws, as well as a Revenge special and Max Malicious Moonsault, its Final Smash.

Piranha Plant, from Super Mario
A completely unexpected character has been added to the game's roster: Piranha Plant, an enemy from the Super Mario series. It will be available via DLC to those who buy the game's digital version or register the game cartridge on the My Nintendo website. Piranha Plant will be available to players until January 31, 2019.
Another new feature revealed for the game is spirits. Spirits can help players increase their power level and can be customized for use in whatever way best assists the playable character. Spirits can enter the battle as secondary fighters, seeking to help the fighter in any way possible. Characters from the Sonic series, including Blaze, Tails, Infinite, Metal Sonic, and the Chaotix, have been confirmed as part of the spirit class.

Spirits being used by the characters.
According to Nintendo, using a spirit is similar to using a talisman or accessory in an RPG. It is a way for players to have fun with more characters, even if those characters are not playable.
Assist Trophies are also back, bringing new characters such as Guile from Street Fighter, Akira Yuki from Virtua Fighter, and some series mainstays such as Shadow the Hedgehog.

Shadow being used as an Assist Trophy.
To end on a high note, Nintendo also showed a preview of the game's story mode, which involves the characters fighting a new threat named Galeem. Story mode begins with Kirby, the only survivor of the villain's attack, and follows his progress as he tries to bring back everyone corrupted by the villain. The trailer also revealed the game's theme song, which features vocals.
Sakurai also said that he intends to release DLC for the game in the future, aiming to expand the character roster even further.
Super Smash Bros. Ultimate will be released for Nintendo Switch users on December 7.