Strez Strez ( ; original spelling : ) ( fl . 1207 – 1214 ) was a Bulgarian " sebastokrator " and a member of the Asen dynasty . A major contender for the Bulgarian throne , Strez initially opposed the ascension of his close relative Tsar Boril . He fled to Serbia , where he accepted the vassalage of Grand Prince Stefan Nemanjić , and Serbian support helped him establish himself as a largely independent ruler in a large part of the region of Macedonia . However , Strez turned against his suzerains to become a Bulgarian vassal and joined forces with his former enemy Boril against the Latins and then the Serbs . Strez was murdered amidst a major anti - Serbian campaign under unclear circumstances in a plot that likely involved Saint Sava . Throne contender and Serbian vassal . Nothing is mentioned of Strez until the events in the wake of the sudden death of Tsar Kaloyan ( 1197 – 1207 ) during his siege of the Crusader - held Thessaloniki . Just like Alexius Slav , another noble who would later emerge as a separatist , Strez was a nephew of the Asen brothers Peter , Ivan Asen and Kaloyan , who were the first three emperors of the Second Bulgarian Empire . However , it is unclear whether through his relation to the early Asens he was a first cousin or a brother of Boril ( 1207 – 1218 ) . At the time of Kaloyan ' s death , Strez was in the capital Tarnovo , perhaps seeking to capitalize on his ancestral rights to the Bulgarian crown . However , Boril proved to be the more ambitious candidate . Boril persecuted the other candidates for the throne , and Alexius Slav , along with Ivan Asen ' s sons Ivan Asen II had to leave Bulgaria . As happened to other members of the royal family , Boril ' s ascension forced Strez and his closest supporters to flee , in that case to neighbouring Serbia , where he was welcomed by the reigning Stefan Nemanjić ( 1196 – 1228 ) in 1207 or early 1208 . Even though Boril requested the extradition of Strez to Bulgaria , the Serbian ruler hoped to use Strez as a puppet in gaining Bulgarian - held territory . Stefan believed that Strez ' s royal ancestry and imperial aspirations would make it much easier to impose Serbian rule over Macedonia , Kosovo and Braničevo , as well as Belgrade , all captured by Bulgaria under Kaloyan . At the same time , Boril was unable to take military action against Strez and his Serbian patron , as he had suffered a major defeat at the hands of the Latins at Plovdiv . Stefan went as far as to become a blood brother of Strez in a ceremony which Stefan was hoping would secure Strez ' s loyalty . In 1208 , Strez headed a Serbian force which seized much of the Vardar valley from Bulgaria . He established himself as a Serbian vassal at the Prosek fortress ( near modern Demir Kapija ) , formerly the capital of another Bulgarian separatist , Dobromir Chrysos . By 1209 , Strez ' s realm spread over much of Macedonia , from the Struma valley in the east , where he bordered the lands controlled by Boril , to Bitola and perhaps Ohrid in the west , and from Skopje in the north to Veria in the south . While Strez quickly gained the support of the local Bulgarian population and possibly inherited the remaining administration from Boril ' s rule , Serbian units nevertheless remained in his domains , either to guarantee his loyalty or with the intent to oust him and annex his lands . Bulgarian vassal . Alexius Slav ' s marriage to the daughter of Latin Emperor Henry of Flanders in 1209 was potentially a great danger to Boril , who could be facing their joint forces . Fearing such a coalition , Boril approached Strez , who was at the time gaining more power and was close to complete independence from Serbia . Strez agreed to a union with his former enemy , though only after Boril reconfirmed his complete autonomy . Strez eliminated the remaining Serbian troops in his lands in an act that the Serbs saw as devil - inspired treason . It is not impossible that Boril persuaded Strez through military action , though it is more likely that the union was achieved through negotiations . In the same year , Strez and Boril had come to peace with Michael I Komnenos Doukas , the despot of Epirus . In late 1209 , Strez and Michael may have attempted a joint campaign against Thessaloniki , as they both lost lands to the Latins in what was likely a retaliation raid in late 1209 or early 1210 . The failure of this attack prompted Michael to break away from his Bulgarian allies and support the Latins . In early 1211 , Strez clashed with the Latins and Epirotes at Thessaloniki and required Boril ' s assistance after Michael and Henry invaded the western reaches of Strez ' s realm . In the early summer , the allied Bulgarian army suffered a heavy defeat at Bitola at the hands of Michael , Henry ' s brother Eustace and Bernard of Katzenellenbogen . Even though it resulted in no territorial losses , it prevented Strez from an expansion to the south . In relation to an anti - Bogomil council in 1211 , Strez is referred to as a " sebastokrator " . The title was either conferred to him by Boril as part of their agreement in 1209 , or was awarded to Strez by Kaloyan during his rule . In any case , Boril certainly recognized Strez ' s right to that appellation . There are signs that Strez divided his possessions into administrative units , each headed by a " sebastos " . In 1212 , Strez was powerful enough to be considered one of the Latin Empire ' s chief adversaries , along with Boril , Michael and Nicaean emperor Theodore I Laskaris , by Henry himself . Anti - Serbian campaign and death . After a series of military failures against the Latins , Boril made peace with Henry in 1213 , cemented through two royal marriages . As Boril ' s vassal , Strez joined the Bulgarian – Latin union , the short - team goal of which was a double invasion of Serbia . In 1214 , the forces of Boril and Henry attacked Serbia from the east , while Strez ' s army , deemed in contemporary sources to be " countless " , penetrated Serbian territory from the south and reached the Polog . Facing a major invasion on two fronts , the Serbs were quick to ask for peace . After Stefan ' s envoys to Strez failed , he sent his brother , archbishop Sava ( canonized as Saint Sava ) to Strez ' s camp . Even though Sava ' s diplomacy was of no effect either , Strez died the night after Sava ' s departure . Serbian sources present the death of Strez as a miracle , Strez being stabbed by an angel , though in reality he was very likely murdered in a plot orchestrated by Sava . Historian John V . A . Fine theorizes that Sava may have found supporters among Strez ' s nobles , some of whom had turned against him and organized his murder , only to defect to Serbia immediately afterwards . According to the hagiography of Saint Sava , in his dying words Strez claimed he was stabbed by a young soldier on the order of Sava . While Strez ' s murder meant an end to the Latin – Bulgarian campaign , Stefan did not undertake a campaign into Macedonia due to the proximity of the coalition troops , which had halted at Niš . In 1217 , all of Strez ' s territory was under the Epirote rule of Theodore Komnenos Doukas , though Boril may have controlled some or all of it in the meantime . The Serbs failed to take advantage of Strez ' s death as far as they did not manage to acquire any of his former domains . Assessment and legacy . Contemporary Serbian sources , such as the hagiography of Saint Sava , are highly critical of Strez ' s actions . The Serbs accused Strez of recklessness , drunkenness , ungodliness , treason and cruelty . The hagiography of Saint Sava tells of Strez ' s alleged tendency to have captives thrown from a high cliff into the Vardar River for his and his guests ' entertainment . As the prisoners were falling to their death , Strez would sarcastically shout at them not to get their coats wet . Bulgarian historian Ivan Lazarov dismisses these allegations as slanderous . In his biography of Strez , he hails the medieval ruler as a " true member of the Asen dynasty " and defends his actions due to him being a " child of his time " . Lazarov assesses Strez as a characteristic , vivid personality who put his independence above all . The name of Strez has become a part of Bulgarian folklore , including a legendary account of his life written down as the " Biography of Prince Stregan " in the 18th century or later . At least one location throughout Macedonia was tied by the locals with Strez , whom the folk interpreted as a voivode or hajduk who defended the people against the Ottomans . Some ruins by the Vardar River near Jegunovce west of Skopje were known to the locals as " Strez ' s Fortress " ( Стрезово кале , " Strezovo kale " ) . Even though in reality his capital , Prosek , lay far to the south , the castle at Jegunovce may have formed part of Strez ' s border fortifications , or it may have been the site of his negotiations with Sava and his murder .