Spirits is a new feature introduced in Super Smash Bros. Ultimate that features various characters from Nintendo's history. The Spirit must be fought and then captured. Captured spirits can be used to equip to the fighter to give various effects. This feature seems to replace Trophies, Event Matches and the Customization features from past games.
Spirits are equippable versions of characters. Based on a piece of official artwork, the characters possess one of the fighters in the base game with various unique rules. After being defeated, the player has a chance to collect them if they bypass the shield. Hitting the shield will reduce it for the next time the player attempts the challenge. Spirits consist of 4 types being Attack, Shield, Grab and Neutral. Attack is strong against Grab , Grab is strong against Shield, and Shield is strong against Attack. Spirits can be Primary which provides a large stat boost and can be leveled up or Support which provide various effects. There are also Fighter spirits obtained through Classic Mode that cannot be equipped.
In addition to being equippable, Spirits have various other uses. Spirits can be sent to the real world which leaves behind a core. These cores can be used to create powerful other spirits. Spirits can also be used to feed amiibo and other spirits though spirits used in this way will be lost.
Spirits also use facilities to be enhanced. Spirits can be trained or go on expeditions. Training will increase their levels and give them new styles while expeditions can be used to acquire more items and gold.