The Mnemonic Nexus is the central server unit for Mnemosyne, the central point of self to which all of its satellite Engine Cores are linked via Æthernet.
Located in the Victorianic Arctic Ocean, the Nexus floats in the freezing currents, taking advantage of the arctic waters to dispel the heat of its servers. The majority of the submerged mass is used for predictive computation and cosmic calculation, while the higher floors are dedicated to fabrication, crew quarters, and an embassy. In the innermost court is a vestibule where someone can have an entirely private, impossible-to-monitor conversation with Mnemosyne.
In the event of disaster or emergency, the submerged sections can be deployed in segments and abandoned. The upperdecks and bridge have auxillary boosters and gravity plating which can be activated. There are also several undisclosed weapons and a fleet of counters aboard to react to any possible threats. The crew is operated by the Navy, which is also has the stated job of keeping Mnemosyne in check.
I'm glad the submerged sections don't seem to have a huge crew presence. Imagine just being jettisoned off in a section in an emergency.
Thankfully, Mnemosyne takes good care of her crew, and her crew takes good care of her. Nobody wants this guy in charge: