The Spartiate Tellis is mentioned two times in the History of the Peloponnesian War by Thucydides. In 2.25.2, he is introduced as the father of Brasidas, a Spartan officer who achieved a minor success in first year of the Archidamian War (431). Later, the son of Tellis was to achieve great fame by capturing Amphipolis, and defending it against an Athenian attack led by Cleon (422). When Brasidas and Cleon had been killed in action, the road to a peace treaty lay open. In March 421, the Peace of Nicias was signed. Tellis is mentioned as one of the seventeen Spartans and seventeen Athenians who took the oath and poured the libations.
The fact that Tellis' son was ephor in 430 may or may not suggest that he belonged to an important family. In other words, Tellis may or may not have been an important man before his son became famous.