Alt is short for "alternate character," and is used to refer to a player's secondary character/less commonly used character, as MMORPGs like Retha will allow characters to make more than one character. (The primary character a player uses is often called their "main".) Alt characters are often lower leveled and ill equipped in comparison to a player's main character.

Retha example: Kit's "main" would be her Echo of Archane, Azarel, and her dancer character, Kitten Lovemuch, would be considered her alt. Prowl and Riko who are stuck on their alts and therefore are in the same boat as Kit and don't have access to all their money, equipment, and best stuff.