Isp and Osp are the two talking snakes who sit on the head of the mute demon Mosp.
Mosp, Isp and Osp together make up a Medusa-like creature, with a female humanoid upper body, a snake-like lower body, sharp bone-spears for hands and two snakes for hair.
Isp and Osp seems to have the same kind of personality. They get along with each other but often have a hard time convincing Mosp to their ideas, or understanding what she is doing.
The three were joined together during the Demon invasion of what became the Dimension of Pain. Originally Isp and Osp were snake-like demonic archers, both known as Asp. They were sent to kill Amospia (Mosp), but became physically joined with her when a wizard cursed her for betraying the dimension to the demonic armies.