The Bodai Shin, whose name translates to mean the Killing Shadows though in Japanese it means The Awakened of Illuminated Mind and Spirit, were a secret order of assassins of which little was known.
In terms of structure, it was suspected that this order of assassins were arranged around in a similar pattern as those of ancient Terran ninjas on Earth. This included not only a clan-like structure but the recruitment of young children into their ranks. This stemmed down the concept of them believing in honor and respecting worthy opponents that were capable of challenging them in armed combat. Rather than make use of energy weapons, the Bodai Shin relied mostly on swords but for a ranged weapon they did make use of shurikens. Furthermore, it was stated that this sect of elite killers were capable of striking large population centers or even starships in order to kill their target. In regards to tactics, the group made use of deception such as holograms to distract allies of their foe but also prided themselves on being masters of disguise. Furthermore, they seemingly made use of suicide attacks using fighters that rammed into an enemy ship though the assassins themselves were quite skilled in surviving such a crash.
They believed in an entity known only as the Void which they saw as a deity of darkness that judged beings that were worthy of life or whether its judgement of them was death. Individual Bodai Shin warriors did not fear death and in fact believed that it brought them a step closer to the Void. An emissary of this being was known as the Herald of the Void who was known as Caliginous. Furthermore, the members of the order detested any forms of weakness be it from healers or telepaths. In fact, they reveled in the fact of turning such individuals against their natures such as forcing a healer to kill. Though they were ruthless in combat, they were not without feelings as parents often attempted to bring back their children if there was a chance for their survival. A unique aspect of their emotional control was that they were felt as voids to telepaths and empaths which masked them from detection. Being well trained, they were able to determine if a person was one of them by simple body movement.
Technologically, the Bodai Shin were quite advanced and made use of high-tech armored suits that masked their features. These suits of armor were capable of cloaking individual assassins allowing them to walk amongst average citizens without being seen. However, the suits of other Bodai Shin were able to detect one another which prevented anyone from using such a trick against them. Another noted weapon within their arsenal was Chaos code which was a type of virus which infected computers and overloaded the systems present.
The infamy of the Bodai Shin meant that they were considered myth and legend to many in the galaxy. In fact, their existence was only confirmed in the mid-24th century by the United Federation of Planets. This came after a scientist of the Federation was brutally murdered by the Bodai Shin and it was suspected that they were targeting another researcher by the name of Doctor Hisharo Noguri. In order to prevent this, Starfleet dispatched the USS Enterprise-E under the command of Captain Jean-Luc Picard to protect Dr. Noguri who was stationed at the Nydaris colony. The doctor in the mean time began researching the Bodai Shin and his notes often linked their concepts to those of Earth ninjas. When Captain Picard arrived on the planet, Dr Noguri dismissed his attempts at saving him as he believed it was impossible against the Bodai Shin. Shortly afterwards, the assassins struck and whilst the Human doctor managed to escape initially - he was ultimately slain by the Bodai Shin. However, it was quickly revealed that the Bodai Shin were not targeting Dr. Noguri but rather Captain Picard along with his crew. Picard was in the mean time assisted by his contact who he was surprised to learn was Sela, a Commander in the Romulan Star Empire.
Over the course of events, the Bodai Shin managed to initially distract the USS Enterprise with holographic attacks but later crashed one of their fighters into the Sovereign class vessels shuttle bay - destroying it in the process and whilst the pilot was believed slain, he was in fact alive and later attacked Deanna Troi. The warrior attempted to break Counselor Troi mentally until she managed to knock him out and he was detained though he revealed no information to his captors. Whilst the Enterprise was later besieged in orbit, the battle against the Bodai Shin assassins continued on the surface which culminated in a large battle. During the fight, Captain Picard attempted to bargain with his attackers by offering the life of one of their children who was saved inside a transporter chip. This prompted the arrival of the Herald of the Void, Caliginous, who claimed that a dark crusade was coming in the future and that he had judged the crew of the USS Enterprise worthy of continued survival for their willingness to threaten a child to ensure their own survival. The Herald scoffed at Captain Picard's belief that they were superior to the Bodai Shin, destroying the offered chip as he stated that in the coming war, there would be many who would join their ranks. Caliginous recalled the Bodai Shin and the battle ended which allowed Captain Picard to return to his ship with Dr Noguri's research. However, once he was back on board the Enterprise, Picard revealed that the chip containing the child's transport program was actually still safe, and his earlier offer had been a bluff. With the girl finding herself unable to feel the Void now that it believed her dead, the crew offered to show her other ways to feel. (TNG - The Killing Shadows comic: "The Trap (Part 1)")