The Slayer Initiative is considered vital towards ensuring the continued safety of American citizens against the HST threat. As such, managing the Slayer Initiative Project is handled by highly-trained professionals whenever possible. Unfortunately, circumstances and staffing concerns occasionally result in less-than-ideal matchups between team members.

The Slayer Initiative is part of OSI's ongoing efforts to ensure the preservation of American citizens from the HST threat. In every generation, one girl is chosen by mystical lot to become the Slayer, receiving superhuman strength, speed, and endurance necessary to combat HSTs on a one-on-one basis, with near-limitless developmental potential. The Slayer Initiative is focused on cultivating the active Slayer, if connected with the OSI, and in preserving the lives of Potentials, those identified as having the highest probability of becoming a Slayer. When possible, a Servator is assigned specifically to train and supervise the current Slayer, and a Servator is also assigned to train and supervise each identified Potential, to ensure that rogue Slayer hazards are kept to a minimum.

The current Slayer is named Anna Caruso. She is presently nineteen years old, and has held the title of Slayer for about one and a half years.

The Slayer power source is not clearly identified in texts; it is generally assumed to be an otherworldly power controlled by a being known as The First Slayer, a quasi-deitific entity that bears a spiritual link to all active Slayers.

Recently, a former Slayer by the name of India Cohen was resurrected from the dead due to the actions of her former Servator, Kit Bothwell. This has had peculiar effects on the current Slayer, Anna Caruso, although it has not caused her death as of this writing. One would assume that when both have perished, the effects of the supernatural empowerment of the Slayer will return to normal in the next Slayer called.

The line of the Slayer has, until the early 1940s, been preserved and jealously guarded by an organization calling themselves the Council of Watchers. However, with the founding of the OSI, competition (of a generally unfriendly nature) has developed over control of the Slayer line.