- This article refers to the assimilated Borg as a species. You may instead be looking for the playable liberated Borg or the Borg Collective faction.
Borg are a cybernetic life-form. Mostly humanoid species have been assimilated, thus almost all Borg Drones have a humanoid appearance. Roughly half of a victim's organic body is replaced by cybernetic implants and nano-technology during assimilation. Since the Borg deem aesthetics to be irrelevant, these implants may very well disfigure and mutilate the subject. During the 24th and 25th century the assimilation process has evolved quickly, leading to ever more extreme forms of replacing host organs and limbs with prosthesis'.
Adaptation and Remodulation
- Whenever an Energy weapon is fired at a Borg, there is a 75% chance of receiving an adaptation counter. Once a player collected 4 of these counters using a particular energy type, all Borg become immune to that energy type from the player's weaponry (adaption counters cannot be received quicker than 0.35 seconds of another, therefore the fastest any weapon can be adapted to is 1.4 seconds; adaption is handled separately for each player, so you will not be affected by your Bridge Officers and/or group members). 
- The act of remodulation clears the "Adapted" debuff. Remodulation is most easily achieved by using a Frequency Remodulator, which can be obtained for free from ship replicators in the inventory. More advanced players may be able to use a Fractal Remodulator, or the final set bonuses from the M.A.C.O, Omega Force, or Honor Guard ground item sets.
- Borg drones that manage to close to within melee range of a player may attempt to use assimilation nanoprobes on them; players who fall below 25% health while under the effects of this will be assimilated and turned into drones themselves. During this state, the player is unable to control their character, who will proceed to attack any nearby friendly players or NPC's until they are defeated. This fate can be averted by the timely use of Immunosupport Nanite Injectors or the Medical Nanite Cloud ability. Vascular Regenerator (Available on Medic and Physician Science Kits) can also be used to remove the nanites.
- Borg at Memory Alpha, the Star Trek Wiki.
- Borg at Starbase UGC, the user-generated-content Wiki for STO.