The author of many works, Aristakes" most valuable contribution in the field of the historiography was his History: About the Sufferings Visited Upon by Foreign Peoples Living Around Us (Պատմություն: մեր շրջապատի այլացեղ ազգերից մեզ հասած արհավիրքների մասին), which described Armenia"s relations with the Byzantine Empire and Georgia and the devastating Seljuk invasions of the 11th century. Once thought to have been born in a village with either the name Lastivard or Lastivert, scholars now believe that Aristakes was born in a village, possibly near the city of Artsn, called Lastiver. Details about his life are fragmented.
As a vardapet, he was well versed in Christian theology and knew Greek and probably several other languages.
He wrote his history from 1072 to 1079, without the support of a patron, recounting contemporary history of which he was an eyewitness. Composed of 25 chapters and a unique colophon, Aristakes describes the Seljuk invasions in 1047-1048 through the capture of Ani in 1064 and the Battle of Manzikert (1071).