Passage 8.27.14
ἔμελλε δὲ ἄρα οὐχ Ἕλλησιν ὁ Βορέας ἔσεσθαι μόνον τοῖς πᾶσιν ὄφελος, τοῦ Μήδων ναυτικοῦ ταῖς Σηπιάσι προσράξας τὰς πολλάς, ἀλλὰ καὶ Μεγαλοπολίτας ὁ ἄνεμος οὗτος ἐρρύσατο μὴ ἁλῶναι· κατέλυσέ τε γὰρ τὸ μηχάνημα τοῦ Ἄγιδος καὶ διεφόρησεν ἐς ἀπώλειαν παντελῆ βιαίῳ τῷ πνεύματι ὁμοῦ καὶ συνεχεῖ. ὁ δὲ Ἆγις ὅτῳ τὰ ἐκ τοῦ Βορέου μὴ ἑλεῖν τὴν Μεγαλόπολιν ἐγένετο ἐμποδών, ἔστιν ὁ τὴν ἐν Ἀχαΐᾳ Πελλήνην ἀφαιρεθεὶς ὑπὸ Ἀράτου καὶ Σικυωνίων καὶ ὕστερον πρὸς Μαντινείᾳ χρησάμενος τῷ τέλει.
Thus it was destined that Boreas would benefit not only all the Greeks by wrecking most of the Persian fleet at Sepias, but this wind also saved the Megalopolitans from capture. For it destroyed the siege engine of Agis, scattering it utterly to ruin by a violent and continuous blast. This Agis, whose attempt against Megalopolis was frustrated by Boreas, is the very one who lost Pellene in Achaea to Aratus and the Sicyonians, and who afterward met his end at Mantineia.