June
Class: Legend Support
Effect: Critical Health Final Smash (Grants a final smash immediately at high damage)
Fighters: Zelda and Junpei
Conditions: The enemy tends to avoid conflict, defeat the main fighter to win
Junpei's childhood friend and main love interest. One of the most important characters in the series, it's only natural to make her the main legend spirit of the board.
Santa
Class: Novice Support
Effect: PSI Resist+
Fighter: Link
Conditions: The floor is frozen
A non-assuming man with an important role in Zero's plan.
Snake and Clover
Class: Advanced Attack
Effect: Battering Items Power+
Fighters: Snake and Villager
Conditions: The enemy becomes stronger after an enemy is KO'd
A brother and sister duo that just can't catch a break. As they're protective of each other, making one stronger without the other during the battle would be a perfect reflection of their relationship.
Sigma
Class: Ace Shield
Effect: None
Fighter: Richter
Conditions: The enemy is injured but powerful
The protagonist of Virtue's Last Reward who, much like Junpei, has a vital role in the nonary game he's participating in.
Phi
Class: Advanced Support
Effect: Jump+
Fighter: Zero Suit Samus
Conditions: The enemy falls slowly
A mysterious girl who appears to have the same abilities as Junpei. She's a great ally to Sigma.
Dio
Class: Novice Attack
Effect: None
Fighter: Roy
Conditions: The enemy tends to avoid conflict
Dio is a very selfish game participant in Virtue's Last Reward. His actions mostly serve to hinder everyone else and can end up killing them, not that he really cares.
Carlos
Class: Ace Neutral
Effect: None
Fighters: 3x Terry, 3x Junpei, 3x Zelda
Conditions: Reinforcements will appear after an enemy is KO'd
Carlos is the team leader for C-Team alongside Junpei and Akane in ZTD and the closest thing to a primary protagonist in the game. He's a team player and achieving his team's ending involves going through several timelines where they're just picked off like flies. As such, I think a spirit battle that reflects this would be kind of funny, where you just kill off C-Team repeatedly until the battle ends.
Diana
Class: Advanced Shield
Effect: None
Fighters: Isabelle, Richter, Zero Suit Samus
Conditions: Take your strongest team into this no-frills battle
Diana is the team leader for D-Team, which includes herself, Sigma, and Phi. A nurse with a pacifist personality, it's no shock that the events in ZTD tear her apart mentally. Despite the odds, she is still determined to get out of her predicament alive along with everyone else.
Zero (Zero Time Dilemma)
Class: Ace Attack
Effect: None
Fighters: Dr. Mario and 6x Metal Mega-Man
Conditions: The enemy is metal,
This Zero comes from the third game in the series. By far the worst and most unfair person to take the role as his plans have world ending consequences, making the parcipants make decisions that will likely leave them dead.