This came out of a few ideas that were thrown around in the comments section for SCP-1235 - I'm not sure at all that it's going to stay in this format and I've even considered switching completely from the 'found document' framework here to a series of vignettes (possibly focusing around the expedition to the dark side of the Earth to retrieve 144): any input highly appreciated.
For reference, 1235 is an anomalous atlas depicting the world in 1903 which when viewed at a sufficient level of magnification is revealed to actually be a perfect copy of the Earth, population and all. Every time it's closed and re-opened the world is 'reset', but the population retain their memory of previous resets. From the perspective of the people of this world, something very bad happened to the universe on 1st March 1903. "Nor shall my sword sleep" is presented in the form of a pre-modern SCP Foundation item entry (see Dr Gears' 001 proposal for the template) - in my headcanon the Safe-Euclid-Keter system was established around 1911. The MC&D connection is something I'm developing - You-Know-Who is Dark, who I consider to have some sort of ability to send messages through time (cf. From The Desk of B. Dark).