Unnamed Borg spheres

List of unnamed Borg spheres.

Battle of Sector 001 sphere
When the Borg tried to assimilate Earth in 2373, the attacking cube was destroyed using Jean-Luc Picards knowledge from his time as Locutus. A sphere left the cube before it was destroyed, and traveled back to the year 2063, in order to prevent the First Contact. It was destroyed by the USS Enterprise (NCC-1701-E), which had followed the Borg through the temporal vortex. 

The remains of the sphere were later found by a group of scientists in the Arctic Circle. A few drones had survived the crash and were preserved in the ice. 

Proto-nebula sphere
In 2375, a transporter accident created a 29th century Borg drone, One. His proximity transceiver contacted a Borg sphere, which intercepted the USS Voyager near a proto-nebula. After initial attempts to fight the sphere failed, One beamed aboard the Borg ship, and navigated it into the nebula. The high pressure inside the nebula caused the sphere to be destroyed. 

"Fort Knox" sphere
In 2375 the USS Voyager destroyed a Borg probe and salvaged a data node from the wreckage. The node contained tactical information about vessel movements in a radius of 30 light years. One ship was a damaged sphere which could only travel at warp 2 due to its encounter with an ion storm. Captain Janeway decided to raid the sphere to obtain a transwarp coil, as part of Operation Fort Knox. The attempt was successful, but Seven of Nine was forced to remain on the ship because the Borg Queen had threatened her that she would assimilate Voyager if she didn't comply. The sphere used its remaining transwarp coil to travel back to the Unicomplex and bring Seven to the Queen. 

Daydream sphere
In 2376, The Doctor enhanced his program so he could experience daydreams. In one of these, a Borg sphere attacked the ship and incapacitated the bridge crew. The Doctor activated the Emergency Command Hologram and took command. He tried to convince the Borg to stop their attack, but the Collective insisted that "You will be assimilated". The ECH then activated the photonic cannon (a fictional weapon of mass destruction) and destroyed the sphere with a single shot. 

Brunali homeworld sphere
In 2376, this Borg sphere attacked the USS Voyager, after being attracted by a false warp signature emitted by a Brunali transport vessel. It tried to assimilate both vessels, but Seven of Nine came up with a plan and beamed a photon torpedo on the Brunali vessel, as it was pulled inside the sphere. The explosion heavily damaged the sphere, giving Voyager the chance to escape. 

Crashed sphere
In 2368, this sphere crashed onto Planet 1865-Alpha in the Delta Quadrant. Only five drones survived the crash (Two of Nine, Three of Nine, Four of Nine, Seven of Nine, and a fifth whom Seven encountered and died in her arms). The drones had to abandon the sphere, because the transwarp chamber exploded.