Avar Khaganate
It is uncertain whether this Altsek can be identified with another Bulgar lord, Altsiok. According to the Chronicle of Fredegar, Altsiok deserted the Avar Khaganate in 631–632. Altsiok settled in Bavaria with 9,000 Bulgars under Frankish king Dagobert I. Altsiok is known to have moved to the Venetian March with his 700 remaining men after Dagobert I slaughtered most of his people.