Not much is known about the D'vor. The Grob claim that the D'vor attacked their home system and killed everyone there.
No one has communicated with the D'vor. Much of what is known about them comes from the Grob -- particularly their ship the Iof, which they captured from the D'vor -- and the captain's personal log from the Leary.
The D'vor have jump technology, energy-based weapons, and energy shields. Humans only have the first of these but the D'vor have managed to miniaturize theirs to the point where they can be used in ships only 20 metres or so long while humans require kilometre-long ships to use theirs.
The Leary's account of their battle with the D'vor is as follows: Most of the ships that came were the sleek sort of design that D'vor ships seem to share, but the first ships seen were of various designs and in worse condition than the D'vor were; these stayed out of the space battle as much as possible and dove for the planets as soon as they could. When the more typical D'vor ships showed up there were lots of small fighter-sized ships, several ships like the Iof, and a larger ship, about 150 metres long, that gave the Leary by far the most trouble: in the end they had to deal with it by ramming it when they'd managed to damage its drive. There were bulkier ships that were obviously transports and a huge vehicle the size of a battleship that had a strange jellyfish-like appearance that was too heavily guarded for them to get close to. The D'vor ships exclusively used energy weapons and seemed to have strange energy-based shields.