This page contains information regarding Star Trek: Lower Decks, and thus may contain spoilers.
Malvus was a Mizarian shopkeeper and the proprietor of Malvus' Goods on Starbase 25. He knew Beckett Mariner from when she lived on the starbase and went by "Becky". They once worked together, which ended with her stranding him on Ceti Alpha IV.
In 2381, Mariner and Brad Boimler visited his shop to ask him the location of the Command Conference afterparty. Malvus, still bearing a grudge for the Ceti Alpha incident, held them at gunpoint until he was disarmed by Boimler talking about the times Mariner had stranded him as well. After Mariner apologized, Malvus agreed to give them the location of the party in exchange for them transporting some crates of limited edition Commander Data bubble bath to storage.
However, Mariner and Boimler were soon stopped by station security. Malvus revealed that he had tipped them to the presence of illegal Klingon disruptors in the crates, which he had hidden there to frame Mariner and have her sent to a penal colony. Mariner and Boimler managed to lose the security forces in a high-speed kart chase, after which Mariner threatened to expose Malvus' plot. At the prospect of sharing a cell with Mariner, Malvus relented and told them the party was in Ballroom Alpha. (LD: "An Embarrassment Of Dooplers")