Silik

Silik was a senior official in the Suliban Cabal during the 2150s. In that capacity, he led the Cabal in fighting on the 22nd century front of the Temporal Cold War.

Temporal Cold War
Silik took his orders from a mysterious humanoid figure who communicated from the 28th century. In exchange for doing his bidding, this individual provided the Cabal with the technical expertise necessary to genetically enhance themselves. These enhancements included shapeshifting, enhanced senses, and the ability to survive in extreme environments. These enhancements gave Silik a distinct advantage over those he opposed.

Encounters with Enterprise
In 2151, Silik sent two of his soldiers to retrieve Klaang, a Klingon courier who carried proof of the Cabal's plot to destabilize the Klingon Empire. Later, as Captain Archer of the was attempting to rescue Klaang from a Suliban helix, Silik engaged in a fight with Archer, nearly killing him. 

As punishment for his failure to start a civil war in the Klingon Empire, the Cabal's benefactor had Silik's enhanced vision removed, but promised to restore it if he succeeded in his next mission. Silik infiltrated Enterprise and attempted to steal a temporal observatory belonging to Daniels, a temporal agent from the 31st century, and deliver it to his master. Silik confronted Captain Archer and attempted to convince him that Daniels was, in actuality, attempting to alter history, and that Silik was attempting to stop Daniels. Silik later shot Daniels with a particle weapon, apparently killing him. He then took the observatory and attempted to flee the ship, but Archer destroyed the observatory rather than let it fall into the wrong hands. Silik then escaped by jumping out of one of Enterprise's launch bays and free-falling into a waiting cell ship. 

The next year, the Cabal attempted to frame Enterprise for the destruction of the Paraagan II mining colony. The Enterprise crew, however, was able to obtain proof of the plot by stealing three data disks from a cloaked Suliban stealth cruiser. On orders from his superior, Silik then led a fleet of cell ships after Enterprise to capture Captain Archer, threatening to destroy the ship if Archer did not turn himself over. Having no choice, Archer agreed, but was then transported to the 31st century by Daniels, who was attempting to protect Archer. Daniels' action had disastrous consequences, however, in that removing Archer from the timeline changed history in such a way as to destroy Daniels's own civilization. This also had the effect of removing the Cabal's benefactor from the timeline, a fact that Silik discovered when he unsuccessfully attempted to contact him. Archer was eventually able to return to his own time, and took Silik as a hostage to ensure Enterprise's release. 

In 2153, after Earth suffered a devastating attack which resulted in the deaths of seven million people, Silik abducted Archer from Enterprise under orders from his master and delivered him to a temporal communications chamber. There, the Cabal's benefactor provided Archer with intelligence that the Xindi were behind the attack, and that they were working for another faction in the Temporal Cold War. This gave Starfleet the information it needed to mount a mission to stop the Xindi from destroying Earth. 

One year later, Silik was assigned to stowaway on Enterprise, when his master learned that Daniels would be sending it back in time to 1944 to stop the Na'kuhl, another Cold War faction, from constructing a temporal conduit. Wanting the ability to physically travel through time rather than just communicate through it, the Cabal's benefactor ordered Silik to steal the conduit's specifications and deliver it back to him. Silik was discovered, however, and eventually teamed up with Captain Archer in order to stop the Na'kuhl. They were eventually successful in destroying the conduit before the Na'kuhl had a chance to use it, but Silik was shot to death in the process. His final words to Archer were an admission that Archer had proven to be a worthy adversary, and he would have preferred to die fighting Archer. 

Background Information
The decision to feature Silik as a recurring character on Star Trek: Enterprise was made even before casting for the part began. A character breakdown sheet which Paramount sent to various talent agents, upon seeking an actor to portray Silik, made clear that he was to be a recurring character and described him as "Late 30s to early 40s. Alien. Physically agile. One of the leaders of the Suliban, a deadly species obsessed with genetic enhancement. Our villain." Silik was later made older, with the script of  describing him as "in his fifties." The character was ultimately played by veteran Star Trek actor John Fleck.

Silik's name was not established until his second appearance,.

Silik's human disguise in was actually John Fleck without the prosthetics usually associated with the part. This marked the first (and only) time in Star Trek that John Fleck has appeared without prosthetics, as all of his previous roles were aliens as well.

Fleck's Borothan costume from the first season episode "Cold Front" was later sold off on the It's A Wrap! sale and auction on eBay.