The ships were equipped with cloaking devices that produced a photonic surge upon deactivation. They also had transporters and could generate a dampening field to drain the power from other ships. They were equipped with powerful directed energy weapons and shields, but were outgunned by Malon export vessels.
In 2375, Voyager was temporarily disabled by three Night Alien ships while traversing the Void. Tuvok illuminated the ships by modifying a photon torpedo into a warp flare. The ships nearly overwhelmed Voyager before they were driven off by a Malon export vessel commanded by Emck.
After Captain Kathryn Janeway made peace with the Night Aliens, several of their ships supported Voyager's attempt to destroy the spatial vortex Emck had been using to dump antimatter waste in the Void. The Night Alien ships weakened Emck's vessel enough for Voyager to destroy it. (VOY: "Night")