Dwer-Da Kal, seen here in a training exercise, before his fall to the Dark Side and adoption of his Sith moniker, Darth Warrigal.

Dwer-Da wields a purple lightsaber, indicating his position within the Jedi Order as a Sentinel. Sentinels are known for their willful blending of the light and dark sides in their use of the force. Well-meaning and non-malevolent in their seeking of balance, Sentinels are nonetheless prone to using excessive force during battle to overwhelm their opponent and end the confrontation quickly.

Dwer-Da is a Jedi Shadow, a sub group of the Sentinels:

A highly respected and secreted group of Jedi, the Shadows went farther than the Investigators in their hunt for the truth. Working closely with the Council of First Knowledge, the Shadows seek and destroy all traces of the Dark side of the Force, and its adepts. While not always present at the Temple, the Shadows were based in the Temple Precinct and reported back as frequently as their mission allowed.
-Wookiepedia

The Jedi Council believed that, despite a Sentinel's usually more hardened resistance to the Dark Side, Dwer-Da's constant exposure to it in his line of work may have tipped the scales in his fall. It is also rumored, however, that his personal contact with an unusually powerful Sith known as Darth Linnaeus may have had a hand in it as well. This seemed to coincide with the death of the Jedi Master who trained him as a Padawan learner, Katsalgi Goucar, another Sentinel Shadow. Interestingly enough, Shadows are known for faking their deaths in order to go deeper undercover in their mission to battle the Dark Side. Some in the Council believe that Goucar could have done this and defected to the Dark side, eventually pulling Dwer-Da with him. Others in the Council dismiss this as nothing more than a paranoid conspiracy theory.
Managed to snag this fantastic YCH piece from Machati-sama on a nerd high after the release of The Force Awakens!

This is not the original you are looking for, move along: http://www.furaffinity.net/view/19056151/

Art©Machati-sama
Dwer-Da Kal/Darth Warrigal©