Mnestra was one of the fifty Danaids (Daughters of Danaus) who took part in the mass marriage to the sons of Aegyptus. Mnestra married Aegius. That night she along with fourty-eight of her fourty-nine sisters slew their husbands.
Punishment
When Mnestra and the other Danaids who had murdered their husbands they were sent to Tartarus and were forced to carry water from the river Styx in a bowls (or jars according to some) with holes over to a tub which leaks at multiple parts. Mnestra and the others were told only when they filled the tub could they wash away their sins. The Danaids continue this essentially impossible task to this very day.
Parents
Danaus & An Ethiopian Women
Ancient Text
"Agaptolemus got Pirene; Cercetes got Dorium; Eurydamas got Phartis; Aegius got Mnestra; Argius got Evippe; Archelaus got Anaxibia; Menemachus got Nelo. These seven sons were begotten on a Phoenician woman, and the maidens on an Ethiopian woman."