Rebuilds appear as a regular enemies in the Arms Depot and the Mechanical Tower. Very few are encountered in the game, but they can be a problem if they're not dealt with quickly. Unlike their previous counterparts, The Creature and Enkidu, these giant humanoids move faster.
Their attacks include:
Advancing while performing a series of punches, ended with an uppercut.
"Assembled from the corpses of many renowned warriors."
Rebuild is a homage to the actual tale of Frankenstein by Mary Shelley. In it, a creature is created by Dr. Victor Frankenstein through reassembling and stitching up many different dismembered body parts and organs from corpses robbed from graveyards, all animated by an unknown process unrecorded by Frankenstein (commonly depicted in pop culture as simple electricity). Unlike the actual enemy supposed to resemble Frankenstein's monster, the Creature, Rebuild seems to take after the original tale, while his counterpart takes after the Frankenstein films.
Along with the Final Knight, this enemy has 666 HP, a number commonly associated with the Devil.