Valina was once a member of the Skeletal Circle, a secret group of Shuggazoom citizens who worshipped the Skeleton King. The leaders, Ma and Pa Sheenko, were her loving yet somewhat critical parents who chose her to accept the Skeleton King's power. Skeleton King's influence saw her fit to rule the Savage Lands, which is a large, hidden jungle which lied in a series of caves beneath the surface of Shuggazoom.
Super Robot Monkey Team Hyperforce Go!
When the Monkey Team and Jinmay attempted to rescue Chiro from the Skeleton King's jungle hidden beneath the badlands, Valeena attempted to kidnap Jinmay, and the rescued Chiro and the rest of the Monkey Team chased after her. She then summoned one of the Dark Ones that was fused with the head and essence of the Skeleton King, in an attempt to destroy the Monkey Team. When the Dark One was injured by Antauri, she lost her power, and was defeated by Chiro. She was tossed into a vat of formless ooze as the savage lands and the jungle beneath it were destroyed.
Valeena returned early in Season 4 only to wind up trapped in a medallion which comes under Mandarin's possession in the same episode. When Mandarin abused her power to create the Monkey Team's worst fears, she trapped him and wanted to use the Skeleton King's skull to resurrect him.
Valeena and Mandarin did, finally, resurrect the Skeleton King at the end of Season 4, but instead of being rewarded by her master, he killed her with a powerful energy blast that reduced her to ashes (though Chiro tried to prevent this).