(covers information from several alternate timelines)
In one possible timeline, the Malkoth were a powerful species native to a region of space near the Krenim Imperium. The Malkoth were erased from history by Annorax's weapon-ship. The only element of their civilization that still exists is a bottle of Malkothian spirits, saved by Annorax aboard his ship. The wine was served at a dinner prepared for Annorax, Chakotay, and Tom Paris in 2374. (VOY: "Year of Hell, Part II") It can be assumed that once the timeline was restored the Malkoth returned to their previous state before Annorax's alterations to the timeline.