2401 Penitent Tangent is the Monitor of Installation 05, referred to by humans as "Delta" Halo. Although it is only shown briefly during the encounter with the Flood Gravemind deep in the bowels of Halo, 2401 Penitent Tangent is nearly identical to the 343 Guilty Spark, another Monitor from the original Halo. It appears to glow a dim red instead of bright blue, and its outer casing may be damaged. It speaks with the same upbeat, artificial voice that all Monitors appear to have, and in the same style as Guilty Spark. Penitent Tangent expresses excitement at the sight of the Master Chief, because a "Reclaimer" can activate the facility and contain the outbreak of the Flood. A short argument with the "deceased" (brought back to life through the Gravemind and unaware he's dead) High Prophet of Regret demonstrates that Penitent Tangent employs the same amount of regulation and protocol when it comes to dealing with the threat of the parasite. This is much to the dismay of Regret, who insists that "...of all the objects our lords [the Forerunners] left behind, there are none so worthless as these Oracles [Monitors]! They know nothing of The Great Journey!!"
Also revealed by Penitent Tangent is the fact that the ring(s) have been activated exactly once before, and are quite capable of being activated again. During the argument with Regret, it expresses dismay that the Flood have been able to spread throughout Delta Halo, saying: "and you know nothing about containment! You've shown complete disregard for even the most basic protocols!". Before anything more can be said, 2401 Penitent Tangent and Regret are taken away, seeing as they were only a tool that Gravemind used to convince the Arbiter of the rings' true nature.
The Halo 2 multiplayer map "Backwash" (part of the Halo 2 Multiplayer Map Pack) takes place in a swamp on Delta Halo. 2401 Penitent Tangent is present on the level and can be heard humming and saying "I am a genius". This is not, however,his voice, nor his tune. It is actually 343 Guilty Spark's hum that is heard throughout the Library of Halo 1.