[Snafu Comics Wiki Source
Before she became the Queen of the Underworld, Mandy lived in Endsville along with her neighbor Billy. On the birthday of Mr. Snuggles, Grim came to take his soul but Billy protested, since he loved him so much. Grim then made a deal to play limbo in Limbo, if he would win he could take all their souls and if Billy and Mandy win he would be under their command. To his surprise he lost from Mandy and thus became their minion.
They experienced many adventures until Mandy began suspecting things. She discovered she was immortal and Grim eventually said it to her after Mandy tried to kill herself. After some time Mandy released Grim so he would be free. Billy died sometime later, but Mandy enjoyed from her immortality. Mandy and Grim would meet each other at times and talked. Mandy grew up and became mayor of Megaville. Grim looked Mandy up and proposed her to marry him, and she eventually said yes. They went on honeymoon and later got a child; Grim Jr. She later also had an affair with Nergal Jr. which resulted in Minimandy. But through all this time she stayed with Grim.
Mandy is the dark angel, the avatar of evil itself. Ever since she first met Grim as an eight-year-old, she had the bonehead wrapped around her little finger. But despite her cruelty toward him, Grim’s feelings for her develop into more than just friendship. Mandy realizes that she is unable to die unless Grim says so, but knows that one day her true time will come, and when it does she will need to make an incredible decision. Now, Mandy is the Queen of the dead, the Empress of darkness and the wife of Death personified. Her two children are nothing like her, but despite this, they look up to and almost fear her as their father once did. Mandy’s blood-red eyes can reduce even demons to pathetic, quivering cowards.