Skulker is the seventh Cardian that Alan and Ann send to gather energy for the Doom Tree. She can trap people inside bubbles, or else shoot thin strings at people to drain their energy. She appeared in Sailor Moon R Episode 7, Much Ado About Babysitting.
When the energy from little kids was not sufficient enough for the Doom Tree, Alan and Ann decided to target babies next, so they sent Skulker to steal energy from the babies. Skulker succeeded on her first attempt, and although one baby, Jordan Winston, escaped the energy drain, his mother's energy was drained, temporarily leaving her and all the other babies in the hospital. Later, Skulker targeted more babies and attempted to steal their energy, but the Sailor Scouts stopped her. Skulker stopped Sailor Venus's attack, but was attacked by the Moonlight Knight, and Sailor Mercury, angry at Skulker for attacking helpless babies, used a new attack: Mercury Ice Bubbles Freeze, and froze Skulker. Sailor Moon then destroyed her with her scepter.
Skulker is portrayed as one of the more evil and hated monsters, due to her draining energy from babies.