He was the regent of Armenia under the young and inexperienced Varazdat, who eventually suspected him of posing a danger to his rule, and thus had him executed, in 377/8.

[7][11] Mushegh, who took part in the battle, wounded the Albanian king Urnayr (a vassal of Shapur II), but allowed him to escape.

[14] When Urnayr returned to Albania, he sent a message to Mushegh thanking him for sparing his life, and also informed him of a surprise attack planned by Shapur II.

[15] According to Ian Hughes, "If P'awstos' numbers are correct, it would appear that for this conflict the entire army of Armenia was gathered to fight Shapur, leaving all other borders undefended – a risk that Pap and Mushegh were willing to take in face of the Persian threat.

[15][17] Mushegh and Terentius then left the hayr mardpet (grand chamberlain) Cylaces (Glak) with an army of 30,000 to protect the border.

[11][19][20] Faustus writes that Mushegh brutally punished the provinces that had revolted against the monarchy, forcing the pro-Persian nakharars to submit to royal authority.

[21] Mushegh is also said to have campaigned against the neighboring kingdoms of Iberia and Albania to restore the Kura River as Armenia's northeastern border.

[31] Varazdat, who was young and impressionable, was by convinced by a group of Armenian nobles that Mushegh posed a danger to his rule, and had played a part in Pap's murder.

Varazdat therefore had Mushegh killed at a banquet and appointed his tutor (dayeak) Bat Saharuni as the new sparapet, in violation of tradition.

[32][33] Mushegh's family and relatives put his body on a high tower, believing that the spirits (aralez) would descend and bring him back to life.