the Golem Visor is a Golem Upgrade from Knowledge Fragment Research.[]
the thaumonomicon says: this metal visor will grant a combat golem a small amount of additional armor protection. it will also ensure that any foes attacked by the golem will drop experience orbs when they die.
This allows Iron golems to, when killing a mob, drop the amount of experience that would be normally dropped when the player killed that mob. This, used in conjunction with the Brain in a Jar can be used to create an experience farm.
Aspects required for researching those are the following:
Cognitio: Learning, Knowledge, Inquiry ( Books, Paper and such )
Tutamen: Defense, Protection, Security ( Armor )
Mortus: Death, Decay, Undead ( Rotten Flesh, Zombie Brain, Bones and Ghast Tears )
Visum: Sight, Vision, Appearance ( Spider Eye, Quicksilver, Carrot and Glowstone Dust )