King Somnus first appears as a handsome young man who is said to rule his kingdom without sleeping. When the Hero becomes a soldier for King Somnus, he is asked to retrieve Ra's Mirror, a magical artifact that's said to reflect the truth.
On the way looking for the artifact, the Hero goes to the "phantom world" where Somnia also exists and the King is a frail old man. Additionally he, along with his wife Queen Apnea, suffer from a illness that forces them to sleep even during the day, never to wake up. This world's King Somnus also had a son who is said to bear a striking resemblance to the Hero, but disappeared.
When King Somnus looks into Ra's Mirror (after the hero retrieved it), it is revealed that he is actually Queen Apnea who had taken the form of King Somnus in the dream world. After you defeat the Dream World Murdaw and use Ra's Mirror on him, he is revealed to be King Somnus of the real world.
When you return to the real world Somnia, the king who had recovered from his illness tells the Hero that in his dreams he was Murdaw and was restored to his real self by Ra's Mirror.