Plucked as a baby from the shores of the Great Salt Lake by Caesar, Dead Sea became legionary from birth and rose to the rank of decanus in 2276. Sometime later, in recognition of his contribution to the victory over the Sun Dogs tribe, a former tribe in the Grand Canyon, his centurion gifted him a machete called the Liberator.
In 2281, the NCR decided that the small town of Nelson would make a suitable base as it could close the hole in the NCR's defenses between Camp Forlorn Hope and Camp Searchlight. Seeing an opportunity to strike before the NCR had a chance to secure Nelson, Caesar sent Dead Sea with two contubernia of legionaries to take the town. After Nelson was taken, Caesar appointed Dead Sea as the commanding officer of Nelson, in charge of keeping the camp clear of NCR forces and instilling a humiliating and demoralizing feeling for the NCR all around.
We Are Legion: Dead Sea wants you to assault Camp Forlorn Hope and execute all of the NCR officers there in order to further demoralize the NCR. Completion of the quest also allows one to gain Great Khans fame and become Papa Khan's heir.
Restoring Hope: The player is given the task to take Nelson back, so that the NCR will control the area. Dead Sea can be found in the Nelson Barracks (your NCR allies will not follow). Then all you have to do is kill Dead Sea.
Dead Sea will give you his unique machete, Liberator, as a reward for completing the quest, We Are Legion. Alternatively, the Liberator can be obtained by killing Dead Sea and taking it from his inventory.
When unmasked, Dead Sea is identical in appearance to Alexus and Gabban.
Though the Collector's Edition playing card depicts him wearing Legion veteran armor, he wears Legion recruit armor in-game.
Dead Sea can see through Legion faction armor disguise, as is demonstrated when asked about attacking Camp Forlorn Hope.