The City of Lost Memories
Part the First: Wandering Thoughts
Deep in the recesses of the ground beneath the Eternal City, below even David's caverns and grottos, there is a lost city. It is dark and dry, and almost begs to be black-and-white, but there is always some color somewhere. It is the City of Lost Memories, created by the Angel of Memory shortly before the Rebellion. It is where memories and thoughts go which have no home.
Anyone entering the City of Lost Memories, which has access routes through a single, forgotten doorway in the ancient Cathedral of the Waters, a domain in the Marches which nobody can remember for long, and a trapdoor under a dusty rug in the lowest level of the castle at the center of the Forbidden City, can see these thoughts and memories as they float about: almost human, or at least animal, in their activity. They take the shape of tall, amorphous, semi-transparent black ghostly figures, and seem to communicate wordlessly or with faint keening sounds. They do retain some fragment of the intelligence that spawned them, and can react to intruders into the city, although they have no more actual substance than a cloud of dust. This presents an interesting problem; although they are nearly insubstantial, they can easily affect their inanimate surroundings, opening doors and lifting objects as anyone else might.
A visitor to the City may, at any time, choose to divest herself of a memory or thought. This requires a Will roll; if successful, the memory simply floats away from the visitor's forehead and takes the form described above. (A failed roll means that the visitor cannot try again to lose that memory for CD hours.)
Residents of the City - that is, memories and thoughts - each have a power level, dependent on their complexity, and ranging from 1 to 12. The memory of receiving a minor paper cut will have a low power level; the Grand Unification Theory will have a high power level (and might even exceed 12). This power level affects not only the physical size of the resident but also its ability to influence the world around it; the memory of a paper cut might be able to open doors, but not much else, while the Grand Unification Theory could affect objects (and potentially other residents) from blocks away, without needing to touch them. The power level of a resident is also equal to its effective Will.
Part the Second: Forget-Me-Not
However, memories consciously removed are not the only denizens of the City of Lost Memories. Although it is not currently known at all, memories "destroyed" by Mental Floss and the Vapulan Brain Scrubber are actually redirected here. (The fact that both artifacts postdate the death of the former Angel of Memory by several centuries would be a curiosity for certain Servitors of Destiny and Fate interested in causality.) Once arrived, they are utterly indistinguishable from any other thoughts or memories in the City. Although no actual testing has been done, it is rumored that no thought memory can actually be destroyed; the lingering power of the Angel of Memory is still so strong that any supposedly-forgotten memories are inevitably drawn to the City.
An odd side-effect of this is that neither Mental Floss nor a Vapulan Brain Scrubber will work at all while in the confines of the City. While a Memory Pearl with a memory already stored in it will not cease functioning, anyone inside the City who tries to implant or extract a memory using a Memory Pearl will meet with possibly unsettling results. The memory being implanted or extracted will attempt to free itself and become free-floating; this requires a Will roll. If the CD of a successful Will roll is greater than the user's Ethereal Forces, the memory breaks free and becomes a regular free-floating denizen (destroying the Pearl in the process); otherwise, the Pearl operates as usual.
Part the Third: Think Of Me
As many visitors to the City have discovered, there is a separate purpose to the City of Lost Memories. Although the thoughts and memories here have a semi-society and are mildly intelligent, a sufficiently willful visitor can consume a free-floating denizen, taking that thought or memory for his own. This requires a Contest of Wills between the visitor and the resident; the denizen has a Will equal to its power level (see above). If the visitor is successful, the memory is drawn into her forehead and becomes part of the visitor's body of thought; if the resident is successful, the resident takes Mind hits equal to the combined check digits of the Will rolls and cannot consume a City denizen until those Mind hits have healed.
Just as removing a memory or thought cannot remove a skill, Song, attunement, or anything else that has been paid for, consuming a resident of the City will not grant anything that requires a character-point expenditure. It might be possible to consume the Grand Unification Theory, but unless the visitor in question already knows physics and engineering, the Theory is just a sequence of numbers and symbols.
In addition, consuming memories or thoughts successfully can still be hazardous. If the visitor wins the Contest of Wills, but the check digit of the resident's Will roll is still higher than the visitor's Ethereal Forces, the visitor gains one level of an Ethereal Discord, which lasts for a number of weeks equal to the resident's power level.
Part the Fourth: Absent-Minded
It is almost universally the case that residents of the City of Lost Memories cannot leave. However, there are occasions when a memory or a thought slips out, either behind a departing visitor or through an improperly closed door. (The doors are warded to keep the residents in; however, if the door is open, the ward is broken.) Denizens outside of the City quickly but slightly change shape; they remain amorphous, transparent, and black, but gain the appearance of a face in the shape of a stylized mask. Thoughts and memories in this form are known across the Orient as No-Faces, and are feared for two reasons.
A loose denizen also is compelled to sustain its newly-physical form; it must consume its original volume (at standard temperature and pressure) in physical material - typically food or living creatures - once every 24 hours. It may stockpile volume, but it loses volume equal to its original volume once every 24 hours at midnight; if it reaches a volume less than its original volume, it dissipates and returns immediately to the City, regardless of its location. The No-Face must make a Fighting attack against the target which is to be eaten, which may Dodge normally; if the attack is successful and deals at least 1/4 the target's current Body hits, the target is eaten. (If the attack is successful and deals at least 0 damage, the No-Face clings to the target and continues to attack once per round; no Dodge is possible at this point, although the victim may use Strength to attempt to pry the No-Face off.) A No-Face can eat an inanimate object without the need to roll.
No-Faces have no compunctions about eating living creatures, which accounts for much of the fear that outsiders have for them. If a No-Face does eat a living creature, it takes on some the characteristics of that creature, including the voice and useful aspects of the form; this is the only way that a No-Face can speak intelligibly.
No-Faces also are compelled to fulfill what they see as their original function, which is their primary focus as memories or thoughts. A No-Face which is a memory of a minor paper cut would be compelled to give people minor paper cuts, while the Grand Unification Theory might feel itself drawn to centers of learning and laboratories. Some of these can be benign - a No-Face whose function is Loyalty would be devoted to anyone who helped it - while others can be entirely malign - a No-Face whose function is the memory of a long and bloody battle would feel compelled to re-create that battle by whatever means necessary.
It is incredibly difficult to kill a No-Face; all damage to a No-Face that does not strike the mask (and, in fact, all damage to residents of the City of Lost Memories) is reduced to 1 Body hit regardless of the attack's Power. (A No-Face can be assumed to have twice its power level in Body hits.) Attacks that strike the mask do damage as normal. When a No-Face or denizen is reduced to 0 Body hits, it dissipates and returns immediately to the City, where it floats unmoving and "unconscious" until it regenerates its Body hits fully (one hit per day). It is possible for a visitor to enter the room of convalescing thoughts, although no resident in the room can be physically affected in any way. (The doorways into the room, for this reason, are devoid of actual doors.)
The City of Lost Memories is specifically designed for the In Nomine setting, although the new mechanics it introduces are entirely generic and may be converted wholesale to any other system with little trouble. In GURPS or the World of Darkness, for example, the hits for a memory are equal simply to its power level. (In the World of Darkness, this represents extra Health Levels.)