Plutarch, Theseus
Bernadotte Perrin, Ed.

Now the sons of Pallas had before this themselves hoped to gain possession of the kingdom when Aegeus died childless. But when Theseus was declared successor to the throne, exasperated that Aegeus should be king although he was only an adopted son of Pandion and in no way related to the family of Erechtheus, and again that Theseus should be prospective king although he was an immigrant and a stranger, they went to war. [2] And dividing themselves into two bands, one of these marched openly against the city from Sphettus with their father; the other hid themselves at Gargettus and lay in ambush there, intending to attack their enemies from two sides. But there was a herald with them, a man of Agnus, by name Leos. This man reported to Theseus the designs of the Pallantidae. [3] Theseus then fell suddenly upon the party lying in ambush, and slew them all. Thereupon the party with Pallas dispersed. This is the reason, they say, why the township of Pallene has no intermarriage with the township of Agnus, and why it will not even allow heralds to make their customary proclamation there of ‘Akouete leo!’ (Hear, ye people!) For they hate the word on account of the treachery of the man Leos.