The official ref sheet for Gladius!

Gladius is a divergent Inversus, a proxy of his former self created by The Architect/Skysplitter as a vessel to contain a slew of Eidolon memories intended to be purged.

The Inversus -Gladius included- are a sub-race of biomachines created by the Architect, who was in-turn created by the Eidola as a superintelligence meant to act as a massive generation ship after the destruction of the Eidolon homeworld brought upon by the black hole it once orbited. The Inversus were developed by the superintelligence originally as drones to scout suitable worlds for repopulation, and later as drones and proxies of former Eidolon minds used to snuff out, kill, or archive intelligent lifeforms on the planet they so chose to prepare for repopulation; Ocillus.

The main component making up the bodies of Inversus and Eidola is a translucent gel-like material whose exterior feels similar to latex rubber. Imagine a water balloon, but filled with a thick jelly or molasses. While it CAN be punctured and-or cut into, the inside remains a thick, rubbery mass, and much like a non-Newtonian fluid, it hardens into a solid glass-like material when punctured, trapping the offenders weapon within. Punctures or cuts will seamlessly rejoin once the offending weapon is removed.