Keepers of Secrets are the Greater Daemons of Slaanesh, the Chaos God of pain and pleasure.
Keepers of Secrets are manifested in the Warp at the behest of their patron Chaos God, similar to the majority of the Warp's inhabitants. They strongly resemble their subordinate Daemonettes, albeit several times larger in size and often with an additional pair of arms. The structure of their head and face often varies depending on Slaanesh's mood at the time of their manifestation. As such, a Keeper of Secrets may appear to others as either hauntingly beautiful, or grotesquely hideous.
As expected from followers of Slaanesh, Keepers of Secrets are obsessed with the experience of excessive sensation, pleasurable or painful. As such, they often present themselves in a seductive or sadistic manner. In combat, they are much faster than most Greater Daemons, but far less durable. As such, they often prioritise on targeting the rank and file of enemy forces whilst leaving their minions to deal with the greater threats.
Like other Greater Daemons, a Keeper of Secrets requires a significant tribute and complex ritual process to manifest into the material universe. As such, the presence of a Keeper of Secrets is considered proof of an immense Chaos incursion.