Form

Various Forerunner forms and rates. From left to right: a Promethean, a Lifeworker, the Librarian, the Ur-Didact's previous form, the Ur-Didact's final form, two unspecified types, a Warrior-Servant, and Master Builder Faber.

Forms were different physical stages assumed by the Forerunners over the course of a lifetime. The Forerunners were able to mutate into various forms through an artificially-induced transformation. Manipular, or Form Zero, was the first and simplest form, assumed by Forerunners at birth. It was noted that Manipulars bore a striking resemblance to humans; however, this would change with higher forms. The original anatomy of a Forerunner would also be distorted when mutating to higher forms, which typically had stiffer facial muscles than Manipulars and thus a more limited capability to convey emotions; for example, with certain higher forms, the ability to smile was lost almost completely. After a mutation, small changes or corrections could be made, but these were mostly cosmetic.

In each mutation, a Forerunner would acquire the genetic imprint of their mentor, typically the individual's father. However, warriors sometimes performed mutations in battlefield conditions, where the imprint would be supplied by one's commander. In rare cases, a brevet mutation could fail and result in deformities; there were rumors that Forerunners whose mutations had failed were sequestered in special enclaves and hidden from the general population. The form one would mutate into was dictated by their rate, as well as the person who performed the mutation. For example, Warrior-Servants were noticeably taller, more rugged and more muscular than Builders, whose forms were more refined. Aside outward appearances, there were also differences in mental and neurological functions. Higher forms of Warrior-Servants, for example, had extraordinary mental abilities; they could absorb massive amounts of information from one another, share sensory input with thousands of warriors during battle, or splinter their perception of time into several "streams."

By roughly 100,000 BCE, a new, more natural mutation pattern had been developed. Instead of being subjected to multiple mutations over several centuries, one would undergo a series of changes over a single year. This would result in fewer inherent physical or mental distortions. Most Forerunners mutated according to this new pattern came from Builder families, with a few Warrior-Servants among them.

List of appearances

• Halo: Cryptum (First appearance)
• Halo: Primordium
• Halo 4
  • Terminals
  • Spartan Ops
• Halo: Silentium
• Halo: Rebirth