Demigod daughter of Helen by Theseus per the Stesichorean parallel tradition, born from Theseus's abduction of Helen at Aphidna and given to Clytemnestra to raise — making the dominant Agamemnon+Clytemnestra parentage a social-paternity coverup of the underlying Helen+Theseus genealogy. The mainstream tradition (Aeschylus, Euripides, Apollodorus) treats Iphigenia as Agamemnon's daughter and would classify her as type=mortal; this entry is the parallel literary tradition that classifies her as type=demigod via two demigod parents (Helen and Theseus), and is the higher-tier reading the registry preserves alongside the mainstream-mortal reading via the parentage-variant. Sacrificed (or substituted) at Aulis to grant the becalmed Greek fleet sailing wind — the sacrifice is the structural pivot of the entire Atreid tragic cycle. Under the Helen-Theseus reading the act is also the mother's war devouring her child via the brother-in-law's sword: the Trojan-War-cause Helen's daughter killed by Helen's brother-in-law to free the fleet that goes to recover Helen.