the messenger

• Vaguely humanoid, horned entity made of mangled, red, flesh-like substance, resembling strands of writhing meat. No facial features, no fingers, no body openings.
• Based on some reports, seems to be totally impervious to any energy-based damage, including kinetic energy. Some tissue damage after contact with strong bases and acids.
• It appears that the demon is able to transmigrate vast distances of space (dozens of parsecs) in an instant.
• Only one instance of outright hostility, when the Herald materialized on the bridge of Osmosis XXIV, killing everyone present in an event classified as the 'Illusory Rapid Decompression'.
• Other than that, it only appeared to convey some kind of cryptic messages to certain individuals. The messages were delivered telepathically and sometimes the 'bystanders' seemed to receive them as well.
• No attempts of retreiving the messages from the recipients were ever successful, no matter what methods of interrogation, suggestion or manipulation were used.
• The 'bystanders' reported strange visions of geometrical structures towering over windswept, colorless wastelands of impossible sizes and the overwhelming feelings of 'absolute loss'. Some also were able to perfectly recall long strings of numbers, sometimes lasting over nine hundred digits. 
• At least one of his appearances is associated with Hexspace. 
• Two of the oldest Artificial Prophets had mentioned the Messenger in their output, often along some incoherent data that would be easily labeled as glitches in any other circumstances (eg. not mentioning the forces of Hell in the same prophecy).
• All reports concerning the Messenger, the properties of his material form and details of his activities are fabricated - Fallen Ones do not interfere with mankind directly and almost never manifest themselves in physical bodies. Consider most of the information above as legends of the Infernal Cults.
• Even the terms 'infernal' or 'hell' or 'demons' are just extreme simplifications, labels given by the feeble human minds, unable to comprehend the entities far more complex and far older than ourselves.
• The Herald comes to those who somehow managed to break the communication barriers and reach out to 'those who serve the Fallen King' (term used in the N'daat Scriptures). There's only a thin line between the H-tip and the D-tip, and the Messenger travels the realms of human slumber with ease.
• It may explain the hallucinatory nature of the reports of his appearance.
• It doesn't explain why the Prophets were mentioning the demon - it only happened once before since the first Iron Pyramid was accessed it became much more common.