The death watch is a mandalorian splinter group.
Its members, under the leadership of Vizsla, fought against Jaster Mereel's "True Mandalorians" during the Mandalorian Civil War. They opposed his reforms and wished to continue to be savage raiders. At least some of them, including Vizsla, wished to start a new Mandalorian War and conquer the galaxy. They wore unique helmets and were led by an "Overlord."
Ill-disciplined to the extreme, they were skilled warriors nonetheless, but constant in-fighting and the egotistical nature of Vizsla's leadership of the Death Watch was its downfall.
When Jango Fett finally defeated Vizsla, the remaining members of the group scattered, and it ceased to have any influence on the galaxy. When Alpha-Ø2 resurrected the Mandalorians, he invited many former Death Watch members to join his Protectors. Other members took up base in the Death Watch Bunker on the forest moon of Endor under the leadership of Teti Viba before he was killed by an unknown raiding party.
[edit] During the Galactic Civil War
A Warrior (a guard of Tungo Li) was seen wearing a typical Death Watch Armor, protecting Tungo Li during the hearing of Janek Sunber
Legacy
The Death Watch uniforms were one of the inspirations for armor of the Emperor's Royal Guard.
As a child, Nashiak Llalik was impressed with the armors of this group. He read a lot about it and entertained his younger sister, Saren, with stories about those armors. As an adult, Saren regretted being separated from her brother, partly because she would have enjoyed those stories again. In 40 ABY, Mandalore Boba Fett believed the destruction of the Death Watch was his father's lasting legacy for the Mandalorians.