Cypsela was a Thracian city on the lower Hebrus river. Unlike many smaller ancient cities on the periphery of the Greek world, it never really vanished. The modern Turkish town of İpsala sits on the site and kept the name. It controlled a major river crossing, and the Romans later ran the Via Egnatia right through it. In the Classical period it belonged to the Odrysians, and Cypsela was one of their key inland cities. It minted its own bronze coins, and may have even served as a temporary royal seat.

Hebryzelmis was an Odrysian king in the 380s BC, and we know very few concrete facts about him. His spot in the family tree is guesswork; some tie him to Seuthes I, but nothing is certain. In fact, everything rests on the numismatic evidence and one Athenian inscription from 386/5 BC, where Athens calls him a friend and benefactor and answers an embassy he'd sent. He was probably shopping for foreign allies in an attempt to shore up his local power. Especially since the kingdom had recently splintered, with rivals like Seuthes II and Amadocus I holding their own pieces.