Mastema

Mastema - the accusing angel; like Satan, he works for God as tempter and executioner; he is prince of evil, injustice, and condemnation.  Cf. The Book of Jubilees and The Zadokite Fragments and the Dead Sea Scrolls, where Mastema is the angel of adversity, "father of all evil, yet subservient to God."  It was Mastema who tried to kill Moses (in the incident mentioned in Exodus 4:24ff.) and who hardened Pharaoh's heart (although, according to Midrash Abkir, it was Uzza who did this).  There is a legend that Mastema appealed to God to spare some of the demons so that he (Mastema) might execute the power of his will on the sons of man.  God apparently thought this was a good idea and permitted 1/10th of the demons to remain at large, in the service of Mastema.  It is also claimed that Mastema helped the Egyptian sorcerers when Moses and Aaron appeared before Pharaoh to perform their magical tricks. [Cf. Beliel; Satan.]  In The Damascus Document, quoted by Vermes in Discovery in the Judean Desert, and angel of hostility is spoken of, and this is applied to Mastema.  (a)

(a) "The Dictionary of Angels" by Gustav Davidson, © 1967