Shadow

Shadows are powerful black phantoms that reside in Kero Sewers. In fact, Shadows are the strongest ghost of Kero Sewers (the weaker ghosts being Hobgoblins and Big Boos). However, despite their strength, Shadows do not fight by themselves; they only aid other ghouls in battle. In a fight, a Shadow will pound Mario's allies with his massive arms, or shoot a physical energy blast at a party member. Additionally, these phantoms know the special attack Endobubble, inducing the Fear status ailment in one party member, thus cutting the character's attack and defense in half. It is highly recommended to use a Pure Water to instantaneously destroy a Shadow.

There is also a sub-species of Shadows called Doppels (who are somewhat related) found in Smithy's dimension.