| Spoiler warning!|
This article contains important details about OFF's plot, which may spoil the game for you. If you haven't played and finished OFF, it is recommended that you do not read this.
The Purified Zones are the Zones of the game after Purification by the Batter. A Zone becomes purified when its Guardian is killed. Upon returning to the Zones, the player discovers that they have become devoid of color and empty, with almost no life remaining. The reason of the Zones being so empty and desolate has been stated to be because of the secretaries killing off any living thing that that crossed paths with these strange baby-like creatures. The layout of the Zones also changes a bit, usually falling apart or becoming unstable and cutting off many areas. The music is also replaced with ominous bells and whispering similar to the Nothingness, along with the occasional sound of someone distantly beating on something and shouting. The sound is similar to a metal door being hit repeatedly, and the voice can vaguely be heard as shouting "Au secours !", which is French for "Help!", suggesting that whoever it is, is trapped within some form of metal room.
InhabitantsZone 2's library, meowing loudly and sadly in an attempt to find his dead brother Valerie.
The Elsen is also found in Zone 2, in a safe-house in the Residential Area.
Secretaries are a powerful type of enemy that appear through random encounters. Described as diabolical, humanoid figures, they appear to be mutilated, deformed babies that attack through screaming and have math-related attacks such as "Divide by zero". The Secretaries appear more strange and mutilated in Zone 2, even more so in Zone 3. The Secretaries also get more powerful in each Zone.
Hidden in each Purified Zone is an Element, a collectible item associated with one of smoke, metal or plastic. The elements are always found in a room with two chests, a Red Cube and several spades on the wall. The element of meat can only be purchased from Zacharie near the end of the Room. The element of sugar can only be obtained once the other Elements are obtained, by defeating Sugar in Zone 0. Once the Elements are all obtained, they can be given to Zacharie in Zone 0 for either the Ashley Bat, the most powerful weapon in the game (which hits twice per physical attack) or the Aries Card, which unlocks a secret third ending.
- The Secretaries all appear to be in a fighting stance similar to that of a boxer. Which means they may be related with the Boxxer in Hugo's "Panic in Ballville" comic.
- While the Zone 3 Secretaries' game sprite makes their face look horribly mutilated, the concept arts show that they're actually wearing a luchador's mask.
- The secretaries look like babies born with a syndrome called Arthrogryposis, this is more noticeable in the concept art.