She is a muscled and imposing brunette who is about six feet tall, leggy, chesty and slim-waisted, handsome rather than beautiful. She looks like a bodyguard from some bad spy movie. Her face is a little too witchy-looking for Anita's tastes.
Like Janos, who presumably made her, Pallas is a rotting vampire. When she rots, her skin and flesh slough off her in wet globs, leaving behind greenish slime. When she touches anything, she leaves behind slime and bits of herself. She doesn't smell, however.
When we first meet Pallas she is wearing black leather and her hair falls free around her face. Later she's clad in a long black dress with a fine webbing of back straps covering her back, and her hair is in a looping braid to one side of her face.
Pallas and Bettina guard the two girls Serephina has had brought in for entertainment for Jean-Claude's visit. They are to whip the girls unless Jason and Larry agree to take their places. The boys agree, but Jason's part is changed into having sex with both Pallas and Bettina right there with everyone watching. He hesitates, but goes along with it, and seems to even enjoy himself until they allow their flesh to rot and decompose in the middle of the act.
When the fighting starts Pallas and Bettina abandon Jason and go for Anita instead. She fires point-blank into Pallas's chest, which makes her stagger but not go down. Another shot into her skull makes her collapse. Afterwards Jason tears into both Pallas and Bettina with his bare hands and scatters bits of them widely around the floor.
Later, when Janos leads a group of vampires to the graveyard Anita and Larry are at, to bring them to Serephina, we learn that Pallas indeed didn't die despite having been ripped to pieces, as the pieces weren't burned afterwards. Anita and Larry are unable to stop Pallas and Bettina from killing Mr. Stirling, but at Anita's request Pallas puts him under for the draining. He regains his senses for a moment just before the end, but a comforting gesture from Pallas quenches the fear from his eyes. The last remains of life within him drain away along with the fear. After Jean-Claude arrives and promises to accept the 'invitation', Pallas, Bettina, and Janos all take into air to make their way back to Serephina.
At the party, the trio stands guard behind Serephina's throne. Serephina has plans to give Jason to Pallas and Bettina, who are supposed to teach him to enjoy rotting flesh. When the fighting starts, Larry keeps firing at Pallas and Bettina, but his silver bullets have little effect. His cross keeps them a little out of reach, though. After Anita wakes up from Xavier's control, she finds that Pallas is one of the vampires who have piled on Jean-Claude to keep him lying down.
When Anita wakes up at the Bloody Bones restaurant, she finds Pallas and Bettina snuggled around Janos on the floor, in their daytime death. Pallas is presumably killed when the building is burned down around her.