Reaper is the carrier of souls to the underworld. She takes the souls of the fallen enemies, who later follow her around like familiars, providing defensive and offensive aid to her.
Reaper is exclusive to the Nintendo Switch edition and is readily available without the need to unlock.
Rules and Restrictions
She herself plays like a default character, with almost no restrictions. However all the enemies she kills (all enemies that would normally drop gold) becomes a soul that follows Reaper around. The souls are weak and vulnerable to attacks and will die to any attack alongside other ways of getting damaged such as bombs and rolling barrels. They will try to remain in the same position Reaper created them, relative to Reaper; i.e. if Reaper kills an enemy one space above, its soul will travel with reaper on the space directly above her. The souls can attack enemies by moving into them (dealing 1 damage regardless of any attack boosts Reaper may have) and if they kill enemies they too become souls. This way, in a very short time Reaper will acquire an army of souls to company her. They are useful for area control, and can attack enemies out of range of the Reaper herself. The souls can also be positioned by their own attacks, ie; if Reaper moves in a direction, and an enemy is in a soul's path in that same direction, she will move and the soul will attack while remaining still.
If Reaper appears at the beginning of a floor and any souls are already overlapping enemies, they will both be unharmed until one of them moves (away and back again). When Coral Riff's tentacles appear around Reaper in phase 1 of that fight, any souls they overlapped will be killed. Enemies in Death Metal's fight seem to harmlessly overlap Reaper's souls if they spawn or teleport on top of them. Other sources of spawning and teleportation are currently untested.
The souls can activate Mimics from a distance, and are able to attack and defeat various Zone 4 enemies (at least Blademasters, Warlocks, and Ooze Golems) without triggering any of their special abilities. They can also attack from inside walls, and can for example defeat Spiders this way. Roofpigs will not activate for them, but Gargoyles will. Monkeys can attack and destroy them even though their attacks usually deal 0 damage.
Since no monsters drop gold in Training mode, no monsters will become souls for Reaper in Training mode.