so I'm rereading Immortal Men in preparation for updating the Metahuman page on DC's wiki and the most obvious thing slapped me in the face:
this is The Constant of the House of Knowledge (self-evident) and one of the 5 original Immortals of the Bear Clan; he has a sun for a face. this got me thinking, I think Duke Thomas directly descends from the Constant.
First of all, he's obviously one of the first 6 metahumans, meaning he is likely the ancestor of at least 1/6th of the metahumans in earth already, but there's a clear golden-yellow solar visual motif going on with his mask-headdress thing, which he shares with Gnomon, who also is an immortal (remember, due to his biological connection, Duke could sense Gnomon telling the truth).
Duke, his mother (Elaine Thomas), and Gnomon seem to have a familial disposition for photosensory powers, abilities that would fit right into the House of Knowledge, who seek information and knowledge.
then there's also this panel where we see The Constant observing the construction of (presumably) the Great Library of Alexandria
you see, each house traveled to, influenced, and implemented their philosophy for mankind in a different region of the world; Conquest to the Roman Empire, Expression to the Vatican in Italy, Harmony to Bodh Gaya (seen under the Bodhi Tree, implying an influence on Buddhism), and Action having an influence on America (it's a little unclear). Now, as a Nigerian with a love of both comics and pre-colonial African history, nothing irks me more than when people lazily only think to use Egypt as pretty much the only example of pre-colonial civilization in Africa BUT, in this case, it's a handy indicator of what region of the world is domain of the House of Knowledge - Africa. Which would mean members of his House would likely consist of Africans and the African diaspora, and he (The Constant) himself would likely be black as well. also keep in mind, in the original story pitch for the Immortal Men, The House of Knowledge [then: Wisdom] are scholarly monks who study everything about the world and hoarding the knowledge rather than sharing.
here's my theory, I posit Gnomon is or was either a member or the House of Knowledge, The Constant's direct descendant, child, or (more wildly and unlikely) is The Constant himself in disguise or under an alias. Jim Lee, who worked on Immortal Men early on, did say Duke was meant to cross paths with the Immortal Men down the line, I believe this was how he was meant to connect. if I were to connect the dots here on how they were going to go about this, I think Gnomon was going to be a member of the House of Knowledge who got ambitious and grew tired of only learning about things. so, for whatever reason, he specifically picks Elaine (maybe she has some metahuman ability that is compatible with Gnomon and would result it a stronger child) and breaks off from the House of Knowledge. at which point The Immortal Man approaches Elaine to join him instead of siding with Gnomon but instead she rejects both and escapes to Gotham, with the key to Gnomon's plan; Duke. So Gnomon works on his machinations while he looks for Duke and Elaine. eventually tracking them to Gotham during the events of the miniseries Batman and The Signal.