Playable character in Honkai: Star Rail, appears to be a counterpart of Raiden Mei. Her name is taken from the river located in Epirus, Greece which is said to be the branch of the underworld.
"Lone voyagers in the cosmos are driven by two desires: to tread in the trails of the past, and to forge their own way. But under Their scrutiny... most end up adhering to the former."
A drifter claiming to be a Galaxy Ranger. Her true name is unknown, and she walks the cosmos alone, carrying with her a long sword.
Though aloof and taciturn, her blade flicks out like lashing lightning. And yet, she always strikes with her scabbard, never drawing the sword free.