Enhanceable spirit

Enhanceable spirits are primary spirits that can be transformed into another spirit after reaching level 99.

Enhanceable spirits do not have a trait other than their enhanceability. Once it has reached level 99, an enhanceable spirit can be enhanced, transforming it into a higher-class spirit; typically, the enhanced spirit's trait is not normally available to primary spirits. The enhanced spirit reverts to level 1 after being enhanced. There are 85 enhanceable spirits overall.

Enhanced spirits are always numbered directly after their unenhanced counterpart, with the exception of Rex (Master Driver), who was added via an update long after its counterpart was introduced in the base game. Enhanced spirits always have the same type and number of support spirit slots as their unenhanced counterpart. While some enhanced spirits do have a different series to their unenhanced counterpart, they always remain in the same universe.

Trivia

 * The Fire Emblem universe has the most enhanceable spirits, with 10 in total.
 * ,, , , , and are the only third-party universes represented by a fighter not to have any enhanceable spirits.
 * Of these, Pac-Man and Final Fantasy are the only third-party universes from the base game not to have any enhanceable spirits.
 * However, in the latter’s case, there are no spirits other than fighter spirits in the base game.
 * Zygarde (50% Forme) is the only enhanceable Novice-class spirit whose enhanced form (its Complete Forme) is a Legend-class spirit.
 * All Pokémon universe enhanced spirits are form changes rather than evolution, despite the enhancing mechanic's irreversibility making it more similar to evolution.
 * Banzai Bill, King Boo, Angry Scarfy, and Model ZX are the only Advanced class enhanced spirits. All other enhanced spirits are either Ace or Legend class.
 * All of these spirits are of a different primary type, resulting in each type having its own Advanced-class enhanced spirit.
 * Zelda has more enhanceable spirits associated with her than any other character, with a total of 3.
 * Full Armor X is the only enhanced spirit with less power than its original form when at level 99.
 * Both the "Giant" and "Transformation Duration ↑" effects are given to all main primary types, those being;
 * Mother Brain (2nd Form), Medusa (Kid Icarus Uprising), Petey Piranha, and The Mighty Jinjonator for the "Giant" effect
 * King of Hyrule, Prince of Sablé, Model ZX, and Natah for the "Transformation Duration ↑" effect
 * The Black Knight and Edelgard - Five Years Later spirits are the only enhanced spirits that share the same skill and primary type to also be from the same universe, that being the Fire Emblem universe.
 * Lotus and Travis Touchdown are currently the only DLC enhanceable spirit to not be exclusive to a DLC Spirit Board, instead making their debut in a Spirit Board event.
 * Toad and Boo are the only enhanceable spirits that are not listed under the same series as their enhanced forms.
 * Coincidentally, both spirits' base forms belong to the Super Mario Series.
 * and are the only universes from the original Smash game not to have any enhanceable spirits.
 * Rex is the first spirit to gain the ability to be enhanced through an update. It also makes him the only enhanceable spirit with nonconsecutive numbers.