The Hebitians, sometimes referred to as First Hebitians, were the first civilization on the planet Cardassia, and were the focus of the Hebitian Age. (TNG episode: "Chain of Command, Part II", DS9 novel: A Stitch in Time)
The Hebitians were an advanced sophisticated culture on every level, they used solar technologies but also lived in harmony with nature, valuing the soil and living a sustainable self-sufficient life envied by the surrounding planets. They were a spiritual people, worshipping the deity Oralius, a tradition that lived on into the Cardassian civilization in the form of the Oralian Way.
The Hebitian society eventually fell when Cardassia suffered catastrophic climate change, the rainforests and grasslands transformed into desert and scrubland. Disease killed millions; and the survivors formed the militaristic and expansionist society known as the Cardassians. (DS9 novel: A Stitch in Time)
At some point in early Cardassian history, the militant members of their society enslaved the Hebitians and used them as slave labor in order for them to create a Cardassian Empire that would last forever. This led to them using the slaves to mine the obsidian stone in the Toran mountains after which records of these acts were expunged from the official history files. (DS9 - Prophecy and Change short story: "The Calling")
In 2167, the first ever find of Hebitian loot was in a tomb in what was the ancient Kingdom of Klu'haa on Cardassia. The farmer who found this tomb sold the treasures for food. Within weeks, all the thieves involved were dead from the disease known as viper's eye. The Cardassian government then took to excavating many more tombs. These resources were used to finance attacks on neighboring worlds. When the wealth of their ancestors ran out, they then attacked Bajor due to its mineral wealth. (ST - New Worlds, New Civilizations short story: "The Glories of the Hebitians")
In 2376 a jevonite figure was discovered in city of B'hala on Bajor. This find interested Prylar Eivos Calan a great deal as the material had previously believed to have been exclusive to Cardassia and quantum dating of the artifact proved it predated the Hebitians. (DS9 novel: Avatar, Book One)
Also that year, Dominion shelling of Cardassia opened the oldest known tomb of the Hebitian Age. The artifacts and art at this site suggest that the first Hebitians had Bajoran features. (ST - New Worlds, New Civilizations short story: "The Glories of the Hebitians")