He is mentioned by Fredegar in his Latin chronicle as "dux gente Surbiorum que ex genere Sclavinorum": "ruler of the people of the "Surbi" (Sorb autonym: "Serbja", Serb autonym: "Srbi") from the nation of the Sclavenians". He is the first ruler of the tribe mentioned by name. Fredegar records him being subordinate to the Franks for a long time and then joining the Slavic union of Samo. After the defeat of the Frankish king Dagobert I by king Samo near Wogastisburg in 631 or 632, Dervan declared independence from the Franks and "placed himself and his people under the rule of Samo".