The Handmaidens served The Unspeakable One, helping to prepare his victims for torture.
When Rimmer landed on a Psi-moon, his personal demons and neuroses were incarnated as physical beings. They dragged him away from Starbug and took him to the lair of The Unspeakable One, who was a representation of Rimmer's self-loathing. He was chained to a pillar and left for the beast, until two scantily dressed young women entered the room.
They were both very slim, with curly blond hair and long eyelashes. Their clothes were reminiscent of ancient cultures and very revealing. Rimmer was relaxed and relieved to see them after being handled roughly by the hooded legions, but the handmaidens made him more nervous by tearing his robe away and leaving him in nothing but a loincloth and a pair of socks.
They proceeded to massage oil into his body, which Rimmer mistook for a precursor to sexual manipulation. He promised to give them nothing but his name and rank, but didn't necessarily want them to stop as long as they had a pizza for afterwards. When they started to walk away up a nearby flight of steps, he was worried they were going to start with a flying leap. Instead they told him that they would summon "The Master" and that Rimmer had been prepared for him. Rimmer assumed that the Master needed him slippery and pliant for some reason, but the handmaidens informed him that The Master preferred an oiled victim so that he would be more conductive for the electricity.
They then struck a gong which awoke the self-loathing beast, who emerged from his lair to begin his torture of Rimmer. The handmaidens then departed the room and were not seen again (RD: Terrorform).
It is unclear exactly which aspect of Rimmer's personality the handmaidens represented - possibly his sexual frustration.