Hrostar was second-in-command of the Menoptera expedition tasked with clearing the way for the Menoptera spearhead to free Vortis from the Animus. He, Vrestin and Hrhoonda found Barbara Wright and took her to the cave they were hiding in. Hrostar was stationed to guard her, but she knocked Hrostar over and escaped.
Barbara later returned with the Zarbi, who killed Hrhoonda. Hrostar was captured but Vrestin managed to get away. The Zarbi then tore Hrostar's wings off and put him and Barbara to work at the Crater of Needles.