Wikipedia
Strymonites
The Strymonites or Strymonitai were a tribe of Sclaveni ( Early Slavs) who settled in the region of the river Strymon ( Struma) in Macedonia.
They took part in the Slavic siege of the Byzantine city of Thessalonica in ca. 677. As narrated in the Miracles of Saint Demetrius, they used their light ships to raid the coasts of the northern Aegean Sea, reportedly even into the Sea of Marmara. They may also possibly have assisted in the Arab sack of the city in 904.