Nihydron
The Nihydron were a spacefaring species in the Delta Quadrant native to a region of space near the Krenim Imperium. 

In an alternate 2374, three Nihydron warships joined the  in its attack on the Krenim weapon ship. B'Elanna Torres and Harry Kim were assigned to work with the Nihydron to implement temporal shielding aboard their ships. During the last conflict of the Year of Hell, two of the Nihydron vessels were erased from history by the weapon ship. This timeline was later negated by Kathryn Janeway. ()

Appendices

Background information

Species 10026 ships shown in  are identical to the Nihydron ships shown in .  It's not clear if they are meant to be the same race.

Apocrypha 
Star Trek Onlines Delta Rising expansion reveals that in the restored timeline, the Nihydron were allied with the Krenim Imperium until the Krenim were defeated by the resurgent Vaadwaur.

The Nihydron reappeared in the   A Pocket Full of Lies. The novel depicted a second iteration of Voyagers first contact with the species, since the events of the Year of Hell – where Voyager made first contact with them in 2374 – were erased from history. Seven of Nine identifies them as Species 1184 and they are described as having waxy flesh, small translucent eyes, wide noses, thin-lipped mouths and two large protrusions where a forehead would normally be.

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Species