For the upcoming 5e setting guide, we do have archaeologist as a new background, but you might be able to use this as a baseline for a feat.
Archaeologist
Though most eyes look to the future, the past fascinates you, and you have found wisdom in exploring the ruins of civilizations that fell to disaster, or that gave birth to today’s world. Foremost in the public’s consciousness are the prehistoric orcs known as the Ancients, who left massive stone edifices, fantastic golden treasures, and little else. But you might also study the Demonocracy, the brief philosopher state of Pala, pre-Malice Elfaivar, the magically unstable ruins of Methia, or any of the multitude of obscure peoples of the past. Perhaps some day you’ll explore the planets above and the ruins of surely long-dead cultures there.
Proficiencies: History, Survival. Cartographer’s tools or navigator’s tools. One modern language and one historical language of your choice.
Equipment: A wooden case containing a map to a ruin or dungeon, a bullseye lantern, a miner’s pick, a set of traveler’s clothes, a shovel, a two-person tent, a trinket recovered from a dig site, and a pouch containing 25 gp.
Feature – Historical Knowledge
You can easily assess the monetary value of art objects that are more than a century old, and when you see ruins you can accurately ascertain who built them and for what purpose. Sometimes when you sleep near ruins, you faintly recall dreams of the people who lived there, which might guide you to where to search or dig.
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For a feat, hm, there's a variety of archaeology stuff throughout the AP. Ruins on Axis Island, the witch stuff on Cauldron Hill, Ancient ziggurats -- maybe you could add some ruins in the Malice Lands in adventure 4, and concoct an excuse for the party to go check them out when they're in Orithea -- maybe some lore about the Lost Riders and their relationship to the radical eschatologists, dragon stuff in Ber, lich and Knutpara stuff in Drakr, all manner of Elfaivaran ruins, lore about the fey titans.
But what sort of special ability could be useful in dealing with those? Hmmm.
