Eighth Brother

The Eighth Brother was an Imperial Inquisitor who was charged in finding the long-forgotten Sith Lord Darth Maul but instead encountered the Jedi company of Kanan Jarrus, Ezra Bridger, and Ahsoka Tano. Maul teamed with the Jedi and battled the Eighth Brother along the Fifth Brother and Seventh Sister.

He was the fourth Inquisitor to appear in the show Star Wars: Rebels. His appearance was his first and last and most shortest in the series. He was masked whole time but he was a Terrelian Jango Jumper.

Serving the Empire
The Eighth Brother served the Galactic Empire and was trained as an Inquisitor in the ways of the dark side under Darth Vader's watch. The Eighth Brother was already an elite fighter and agile warrior since his species allowed him to leap to extreme lengths. After the death of the Grand Inquisitor, the remaining Inquisitors consisting of the Eighth and Fifth Brothers and Seventh Sister were charged by Lord Vader to search the galaxy for any surviving Jedi who escaped Order 66.

Search for the Shadow
While the Fifth Brother and Seventh Sister followed the trail of a group of Rebels across the universe, the Eighth Brother was given a new task by Lord Vader under the orders of the Emperor to search for Darth Maul whom was identified as the Shadow and eliminate him. The Eighth Brother later traveled to the planet Malachor and found the Shadow hiding beneath a Sith temple and confronted him. He instead encountered the Jedi group of Kanan, Ezra, and Ahsoka and stalked them for a bit until attacking and separating Ezra from the others.

The Eighth Brother was forced to retreat but was pursued by Kanan and Ahsoka. He was unable to escape because their droid sabotaged his TIE fighter and was captured and questioned by the Jedi. While being questioned, he managed to send out a signal to the Fifth Brother and Seventh Sister for aid. They later arrived and freed him and together attacked the Jedi and managed to outnumber them for a bit until Ezra arrived with the Shadow revealed to be Maul. The former Sith and Jedi battled the Inquisitors and forced them to temporarily retreat.

Defeat and Death
The Inquisitors later discussed the potential threat of Maul possessing the Sith holocron that was sought by Darth Vader, recklessly the Eighth Brother left the pair to reclaim it. He attacked Kanan and Ezra and managed to knock Kanan out and tried to attack the boy before Maul and Ahsoka arrived and drove the Eighth Brother away. Teamed with the Fifth Brother, they attacked Kanan and Ahsoka while the Seventh Sister engaged Ezra and Maul.

Maul managed to kill the Seventh Sister and later the Fifth Brother while Kanan damaged the Eighth Brother's lightsaber. Outnumbered and outmatched, the Eighth Brother attempted to flee using his spinning lightsaber blades to fly away as he leaped from the top of the temple. The weapon malfunctioned and sent him falling to his death.

Trivia

 * The Eighth Brother was the fourth Inquisitor introduced and the only one not to show his face.
 * Had the shortest presence in the series debuting and dying in the same episode.