The Borg of the Mirror Universe in Star Trek are a major power that we never get to see in canon, but there is some lore on them mentioned in books and games, so let's take a look at what the Terran Empire has to contend with, not the Collective, but the Borg Kingdom.

Star Trek Online developed by Cryptic Studios and Perfect World.
Star Trek Picard/Strange New Worlds/Enterprise/Voyager/Deep Space Nine/Discovery and The Next Generation are all owned by Paramount Pictures/CBS and distributed by CBS.
This Video is for critical purposes with commentary.