90-forms were the first generation of timeships engineered for specific military purposes. They appeared as large faceless spherical masses, and they moved gracelessly and unsubtly. Their pilots were groomed to stay neurally linked to the machinery for centuries on end, with any regeneration in that time "welding" them further into the hardware.
90-forms were sanctioned by the Presidency twenty years before the start of the War. Rather than direct hostile action, their intended purpose was to block off routes through time by extending their mathematical masses into the universe's causal connections. The first few 90-forms patrolled the perimeter of Dronid's noosphere, marking out the cross-dimensional battlefield of the conflict to come, just days before the battle. (PROSE: Timeships)