...oh damn. Acheron is a great choice. Especially the POWER the has. Its honestly an amazing choice.
I hope it gets picked.
Since Apeiron is a Greek name and means Unlimited or Primal Principle of All Matter, I think that the closest 5 sidekicks Apeiron has could be named after the 5 Rivers of the Underworld....heck you know how badass sidekicks or teammatea are, when they have their own team. Just think about it
Random Villain Cape 1: "Oh shit, that is one of the Five Rivers!"
RVC 2: "The what?"
1: "One of Apeiron's Five Rivers of the Underworld, we have to get the hell out of here!"
So far we have:
Lethe: The River of Forgetfulness and personification of Oblivion, daughter of Eris. Those that drank from her waters would lose all memories from their previous existence, one step needed for reincarnation. Holder: Aisha Laborn.
Acheron: Also known as The River of Woe, the roman poet Virgil called it the principal river of Tartarus, from which the Styx and Cocytus both sprang. The newly dead would be ferried across the Acheron by Charon in order to enter the Underworld.
Styx: Also known as The River of Hatred, although Styx, the word, literally means "shuddering" and expresses loathing of death. In Homer's Iliad and Odyssey, the gods swear by the water of the Styx as their most binding oath.
Plegethon: The River of Fire, in the Percy Jackson books its waters keep the wicked alive, so they can continue suffering in the Fields of Punishment. It's name means flame, or Fire-flaming if you use Pyriphlegethon, the second name.
It is said the waters of the river can burn away the sins of a mortal sent to the Fields of Punishment, but only if they are truly remorseful of their past actions.
Cocytus or Kokytos: which literally means "Lamentation". The River of Ice, in Dante's Inferno, the river in which those accused of Betrayal or any form of Fraud, get punished by being buried in the ice by various degrees.
I mean, the connotations of anyone naming themselves after one of these Rivers are strong