Pausanias, 1.43.
“They also say that there is a hero-shrine to Iphigenia—for she died there, according to the Megarians. But I have also heard another report circulated by the Arcadians and I know that Hesiod wrote in his Catalogue of Women that Iphigenia did not die, but thanks to Artemis is actually Hekate. What Herodotus wrote agrees with these things—that some who live near Skythia sacrifice survivors of shipwrecks to a maiden and they say that the maiden is Agamemnon’s daughter.”
λέγουσι δὲ εἶναι καὶ ᾿Ιφιγενείας ἡρῷον· ἀποθανεῖν γὰρ καὶ ταύτην ἐν Μεγάροις. ἐγὼ δὲ ἤκουσα μὲν καὶ ἄλλον ἐς ᾿Ιφιγένειαν λόγον ὑπὸ ᾿Αρκάδων λεγόμενον, οἶδα δὲ ῾Ησίοδον ποιήσαντα ἐν καταλόγῳ γυναικῶν Ιφιγένειαν οὐκ ἀποθανεῖν, γνώμῃ δὲ ᾿Αρτέμιδος ῾Εκάτην εἶναι· τούτοις δὲ ῾Ηρόδοτος ὁμολογοῦντα ἔγραψε Ταύρους τοὺς πρὸς τῇ Σκυθικῇ θύειν παρθένῳ τοὺς ναυαγούς, φάναι δὲ αὐτοὺς τὴν παρθένον ᾿Ιφιγένειαν εἶναι τὴν ᾿Αγαμέμνονος.
7.26.5
“The temple is Artemis’ and the statue is made in a technique similar to our own. A virgin serves in the temple—and she is there until she reaches the age of marriage. There is another statue inside which is very old. The people of Aigeira claim it is Iphigenia, Agamemnon’s daughter. If they are telling the truth, then the temple was built for Iphigenia in the beginning.”
᾿Αρτέμιδός τε ναὸς καὶ ἄγαλμα τέχνης τῆς ἐφ’ ἡμῶν· ἱερᾶται δὲ παρθένος, ἔστ’ ἂν ἐς ὥραν ἀφίκηται γάμου. ἕστηκε δὲ καὶ ἄγαλμα ἐνταῦθα ἀρχαῖον, ᾿Ιφιγένεια ἡ ᾿Αγαμέμνονος, ὡς οἱ Αἰγειρᾶταί φασιν· εἰ δὲ ἀληθῆ λέγουσιν οὗτοι, δῆλός ἐστιν ἐξ ἀρχῆς ᾿Ιφιγενείᾳ ποιηθεὶς ὁ ναός.
Etymologicum Magnum
“Iphigenia: Euphorion says she really is the daughter of Helen and Theseus and was secretly given to Klytemnestra. [The origin of her name] is that Helen gave birth [hupogeinato] to her after she was overcome by force [iphi] by Theseus.”
᾿Ιφιγένεια: Εὐφορίων αὐτὴν ἐτυμολογεῖ ῾Ελένης καὶ Θησέως· ὑποβλητὴν δὲ δοθῆναι Κλυταιμνήστρᾳ· οὕνεκα δή μιν ἶφι βιασαμένη ῾Ελένη ὑπεγείνατο Θησεῖ.
For the assertion that Iphigenia was Helen’s daughter, see an earlier post. In the Hesiodic passage mentioned here, Iphigenia is referred to as Iphimedê and is transformed by Artemis into Hekate.
And a somewhat related bit from Pindar:
Pindar, Pythian 11.22-32
“The pitiless woman. Was it Iphigeneia
Slaughtered on Euripus far from her homeland
Who made her raise her anger-heavy hand?
Or was it being tamed by long-nights in another’s bed
That led her to this? For young brides
This is the most hateful error, impossible to conceal
Because of other people’s tongues.
Your fellow-citizens are gossip-mongers.
For prosperity carries with it a proportional envy.
Whoever gasps near the ground moves unseen.
Atreus’ heroic son died
When he finally arrived home in famous Amyklai—
And he lost the prophet-girl too, after he destroyed
The burned homes of the Trojans for Helen”
νηλὴς γυνά. πότερόν νιν ἄρ’ ᾿Ιφιγένει’ ἐπ’ Εὐρίπῳ
σφαχθεῖσα τῆλε πάτρας
ἔκνισεν βαρυπάλαμον ὄρσαι χόλον;
ἢ ἑτέρῳ λέχεϊ δαμαζομέναν
ἔννυχοι πάραγον κοῖται; τὸ δὲ νέαις ἀλόχοις
ἔχθιστον ἀμπλάκιον καλύψαι τ’ ἀμάχανον
ἀλλοτρίαισι γλώσσαις·
κακολόγοι δὲ πολῖται.
ἴσχει τε γὰρ ὄλβος οὐ μείονα φθόνον·
ὁ δὲ χαμηλὰ πνέων ἄφαντον βρέμει.
θάνεν μὲν αὐτὸς ἥρως ᾿Ατρεΐδας
ἵκων χρόνῳ κλυταῖς ἐν ᾿Αμύκλαις,
Γ′ μάντιν τ’ ὄλεσσε κόραν, ἐπεὶ ἀμφ’ ῾Ελένᾳ πυρωθέντας
Τρώων ἔλυσε δόμους