The Netherworld Empresses are a biker gang who only appear in the Disgaea anime. The members include a ronin, an archer, a galaxy mage, a knight, and, strangely enough, someone who has a similar appearance to a male healer, but apparently is a girl, since this person has a girl's voice.
The Netherworld Empresses first appear in Episode 4 (A Solomon-style Judgement at the Dinero Castle) where they attack Laharl and the others and try to claim the 10 million HL bounty that Etna placed on him. Laharl blew them away with his Overlord's Wrath attack, and they never appear again in the rest of the episode.
They also have a bigger role in Episode 7 (Netherworld Siblings). They appear chasing after Maharl, a girl claiming to be Laharl's sister. They follow her into a salloon where Laharl, Etna, and Flonne are eating at. Though Gordon, Jennifer, and Thursday try to get them to leave, they easily defeat them and continue searching for Maharl. Flonne makes it obvious where Maharl is hiding, but they leave after Laharl yells at them for disturbing his meal.
Later in the episode, they send Laharl a note saying they have Maharl. They also kidnapped Flonne, who was told that Maharl had something to ask her. Though Vyers showed up to save Flonne, he left after seeing Maharl, who disturbs him because he overheard her calling Laharl her big brother. Then Laharl and Etna show up to save Maharl. It is then revealed that Maharl was really their leader and they kidnapped Flonne so Laharl would give them the Black Lizard's Tail, the greatest treasure passed down in Laharl's family. However, Laharl doesn't know where it is, since its whereabouts were only known to King Krichevskoy. Instead, he easily defeats the Empresses. Maharl then tries to pass as Laharl's sister again, an effort that fails against everyone except Flonne. The Empresses are shocked at how low she is willing to go, and decide not to let her be their leader any longer. They attack her with a fire spell before leaving.