In the past few weeks, we have discovered that Goliath had a sort of guardian angel figure. Said figure was found out to be initially Gaster-like; fragmented, everywhere and nowhere... And what could have been.
Upon finding all fragments, we were able to confirm that this was another version of him, but from a scrapped concept that could've been used for the story of IRIS; "Under the Vice". He has been named Midnight.
Goliath also had a fragment within him, hence why Midnight was his sort of guardian angel. He still has that connection with him, of course. But now there's a visible manifestation of that connection on him. From the tips of his fingers to his elbows, Goliath now has pulsating, green, vine-like markings.