He was Brother Tiresias's superior at the time that Chapter Master Thrasius returned from planning for the future of the Scythes after their near-destruction by Hive Fleet Kraken. Both Angeloi and Tiresias were openly critical of Thrasius's beliefs on the direction that the Chapter should take, and had rallied much support amongst their battle-brothers.
Suddenly and without warning, Angeloi was sent away by Thrasius to join the Deathwatch, along with more than forty other rebellious Scythes who had been identified as likely to speak out against their Chapter Master. This represented a loss of nearly a third of Chapter's fighting strength.
During his time in the Deathwatch, Angeloi fought many battles against the Tyranids. He was in command of a successful mission to purge the forested planet of Phirus, and saved one of his men from a Lictor during an ill-advised ritualised hunt. Following this mission, he requested to be returned to his parent chapter, but it is unknown whether this request was granted.