Lo and Li

Lo and her twin sister, Li, were Azula's two elderly advisers. Little else is known about her background. Lo appeared to be a cold, focused person who has contributed to Azula's undeniable thirst for power. She and Li had served as Azula's mentors and had overseen her Firebending training, despite not being Firebenders, since the Fire Nation princess was a child.

History
She and Li advised Azula to abandon the Royal Procession in favor of a smaller elite group to better increase her chances of capturing her fugitive brother.

Lo and Li were later seen presiding over a rally held at the Capital city's royal plaza, where she boastfully declared victory over the Earth Kingdom thanks to the efforts of Azula and the newly returned Prince Zuko.

Later, Zuko, Mai, Ty Lee, and Azula stayed with her and her sister on Ember Island where they own a small but comfortable beach house. Lo and Li have been coming to this tiny beach cottage since they were infants. When their parents died, they inherited the cottage. When life in the Fire Nation Capital becomes too hectic, the twins escaped to their little oasis, where they seemed to be a lot more relaxed, rather than as somber and serious as they appear in the other episodes. On one of the walls, a poster shows two very beautiful girls. The kids asked who the young women were, and Lo replied, "Can't you tell? It's Li and me!" Later, she told the kids that the beach has special "powers", supposedly it changes people, smoothing even the roughest edges. After this advice, she and Li clapped their hands and announced that they're going to the beach. They then removed their outer garments, revealing they were wearing swimming costumes underneath. This unexpected display made Mai put her hand over Zuko's eyes.

In light of Azula's recent and frantic purging of the Royal Palace staff, Lo and Li expressed to Azula their concern for her welfare, and she in turn accused the sisters of acting on her father's orders. She ordered the twins to have an Agni Kai, after which the sisters told her that would be impossible since neither of them are Firebenders. She then decided to banish even one of her most trusted allies (Lo), but instead pointed to Li, which led to confusion amongst the two.

Her and her sister's ultimate fate after the War is unknown.

Trivia

 * Lo's name seems to have come from luō luō (羅羅) which translates in Chinese as 'endless mumbling'.
 * It was implied that she and her sister were Firebending Masters, since they were first seen while overseeing Azula during her training in lightning generation. However, when commanded by Azula to fight an Agni Kai, they stated that neither of them are Firebenders. While not Firebenders, they may had been experts regarding chi manipulation and the positive and negative energies used to create lightning.
 * Both Lo and Li had very low earlobes, which was most likely due to their old age, as they were not seen wearing earrings.
 * Both Lo and Li were implied to be able to operate complex machinery, since the creators claimed that the twins piloted Azula's Tank Train.
 * The small triangle that was present on both Lo and Li's hair bands, and also on the Yu Yan Archers head bands, is the alchemical symbol for fire.