Mama

Mama (ママ, Mama, Mana in the English anime series) is the guardian ghost of Opacho.

About
Mama is the guardian spirit of Opacho. Although her true form is not seen in the series, its believed to take the form of a sheep.

O.S. "Ram"
O.S. Ram Description: Using her own hair, Opacho creates an Over Soul in the shape of a sheep around her body. The Over Soul has great offensive power as a single hit from it was able to break all of the bones in Umemiya Ryunosuke's body in the procress.
 * Shaman: Opacho
 * O.S. Type: Spirit Type
 * Spirit Ally(s): Mama
 * Medium: Opacho's hair

Trivia

 * Mama's name is presumably a reference to both of Opacho's mother and Asanoha; Opacho is an orphan, and Asakura Hao was raised by Ohachiyo after his mother died, and Ohachiyo became his first guardian spirit.
 * In the video game Shaman King: Master of Spirits 2, Mama makes an appearance as an enemy in one of the stages leading to the final boss.