Forerunner Super-Heavy Sentinel

The
Vanguard Sentinel, also known as the Super-Heavy Sentinel, is an
automated weapons platform which is only found extremely-important
forerunner installations, such as the Ark and the Halo Array.
The largest sentinels known to date, they carry formidable weapons, the
most prominent being the four heavy hardlight cannons, one on each arm,
and two light hardlight beam emitters beside the main cannons - with
weapons like these, they are assumed to deal with only infestations on a
planetary scale. Like their smaller cousins, they carry equipment that
allows for the repair of damaged systems, transportation of resources
and investigations of atmospheric concentration present on the Halos.
Given their size, role and resource requirements, ordinary sentinel
factories are not up to the task, and are instead manufactured at huge factories rated for ship construction.