Abraham became an Avar khagan around 805.Gerard Labuda: Abraham. In: Słownik Starożytności Słowiańskich. Vol 1. 1961, p. 1. He was the successor of Theodorus.
Abraham was baptised in Germany. He died or was deposed before 811, because in this year, the Avar khagan was his successor.
Footnotes
References Labuda Gerard: Abraham. In: Słownik Starożytności Słowiańskich. Vol 1. 1961, p. 1.
Further reading Kos F.: Gradivo za zgodovino Slovencev v srednjem veku. Vol 2. Ljubljana 1912, p. 29, 39–40.