Darth Tenebrous Speculation

As per Tenebrous’s force powers, he is, as a Banite Sith, extremely powerful. His telekinetic abilities have already been proven to be very potent to the extent where he can shield himself from a massive explosions and hold up very large boulders. He also has shown an aptitude for force lightning, being able to generate lightning that left residual sparks. He also has shown some exceptionally powerful foresight, being able to sense his impending death, though not being able to attribute it to the proper factor. Tenebrous was also mentioned to utilize Bith science as an alternative to Sith sorcery. Given the sensory acuity of the Bith, as well as the skill with numbers and logic attributed to Tenebrous’s race it is likely that Bith science is a very exact thing. Given once again, the sensory acuity of the Bith to the point of it being microscopic, as well as Tenebrous’s experience with retroviruses, it is likely that Bith science has applications in regards to microbiology. Given Tenebrous’s foresight as well as the logic and numbers in regards to Bith and their science, it is also likely that Bith science was also a way to predict and perceive possible outcomes of events. Now that I’ve covered and gone into depth on the powers he’s been explicitly stated to possess, I will now look at powers he likely had based on his other powers and the powers known by his apprentices. Given some of the more manipulative applications of Bith science, as well as the perceptive nature of Tenebrous’s mind, it is very likely that mind tricks fell under his lapel. Another thing to consider as being part of Tenebrous’s repertoire is tutaminus, considering Plagueis’s familiarity with the power, and Tenebrous’s aptitude for energy attacks (force lightning). There’s also a good possibility that Tenebrous could levitate using the force considering his telekinetic prowess and Venamis’s ability to do such a thing. An ability that Tenebrous definitely would not possess would be force scream. Considering how vulnerable the Bith are to sonic weaponry, it would not do well to have the origin of such a sonic burst be himself.

As per his fighting style, he was skilled enough to judge Plagueis to be a master duelist and train Venamis in Plagueis's style and how to counter it. Plagueis's primary style is implied by his actions to be Niman, so training two students in it and how to counter it suggests a high level of competence with Niman. The fact that Plagueis was able to switch styles to combat Venamis suggests that he trained Plagueis in more than one style, implying familiarity with multiple styles. I think it is quite likely that Tenebrous was a master of all seven forms, though I have a few candidates for his primary form. His highly impressive speed suggests that he may employ one of the more fast paced aggressive styles of lightsaber combat, such as Juyo or Ataru. His speculated knowledge of Niman suggests that this may also be his primary style, and this is somewhat supported by his focus on the more arcane aspects of the force. His Bith physiology however suggests Makashi. The acute senses of the Bith suggest that he would be capable of great precision. This is only further backed up by his force enhanced abilities and his genetic studies. Overall I believe Forms II, IV, VI, and VII are the most likely candidates for his primary form, though I'm leaning more towards Makashi than the other three.

As per his armament, he wielded a single lightsaber at the time of his death, so I'd assume that was his standard armament. And he almost certainly wouldn't have any sonic weaponry on him.

As per the manner in which he killed his master I have a theory. Seeing as Tenebrous's master opened up a wound in the force (or was the wound) and risked the exposure of the sith, it is likely Tenebrous was forced to take him down to keep the Sith hidden. This suggests that Tenebrous may have been forced to challenge his master, either being forced to face him in fair combat, or if he was not ready to take him down in fair combat, killing him through other methods avoiding a direct confrontation.

He helped with the very early stages of Plagueis and Sidious's grand plan, likely through economics and coming up with various scientific schemes to take the Jedi down.