 In 804, the Bulgaria conquered the southeastern Avar lands of Transylvania and southeastern Pannonia up to the Middle Danube River, and many Avars became subjects of the Bulgarian Empire.Khagan Theodorus, a convert to Christianity, died after asking Charlemagne for help in 805; he was succeeded by Khagan Abraham, who was baptized as the new Frankish client (and should not be assumed from his name alone to have been Khavar rather than Pseudo-Avar).Abraham was succeeded by Khagan (or Tudun) Isaac (Latin "Canizauci"), about whom little is known.