Passage 2.9.1
Κλεομένης ὁ Λεωνίδου τοῦ Κλεωνύμου παραλαβὼν τὴν βασιλείαν ἐν Σπάρτῃ Παυσανίαν ἐμιμεῖτο τυραννίδος τε ἐπιθυμῶν καὶ νόμοις τοῖς καθεστηκόσιν οὐκ ἀρεσκόμενος. ἅτε δὲ ὄντι αὐτῷ Παυσανίου θερμοτέρῳ καὶ οὐ φιλοψύχῳ ταχὺ τὰ πάντα ὑπὸ φρονήματος καὶ τόλμης κατείργαστο, καὶ βασιλέα τε οἰκίας τῆς ἑτέρας Εὐρυδαμίδαν παῖδα ἔτι ἀνελὼν φαρμάκῳ διὰ τῶν ἐφορευόντων ἐς Ἐπικλείδαν τὸν ἀδελφὸν μετέστησε τὴν ἀρχὴν καὶ τὸ κράτος τῆς γερουσίας καταλύσας πατρονόμους τῷ λόγῳ κατέστησεν ἀντʼ αὐτῶν. ἐπιθυμῶν δὲ πραγμάτων μειζόνων καὶ ἀρχῆς τῶν Ἑλλήνων, ἐπέθετο Ἀχαιοῖς πρώτοις, συμμάχους ἐλπίζων ἕξειν ἢν κρατήσῃ καὶ μάλιστα ἐμποδὼν οὐκ ἐθέλων εἶναί οἱ τοῖς δρωμένοις.
Cleomenes, the son of Leonidas, who was himself the son of Cleonymus, when he had succeeded to the kingship at Sparta, began to imitate Pausanias, desiring tyranny and dissatisfied with the established laws. But being naturally more impetuous and less concerned with preserving his own life than Pausanias, he swiftly effected all his plans through sheer boldness and daring. Having killed with poison Eurydamidas, the king of the other royal line, while the latter was still a boy, through the agency of the ephors, he transferred the kingship to his brother, Epicleidas. Next, after overthrowing the power of the Council, he set up in its place officials whom he termed “Patronomoi” (Guardians of the Fathers’ laws). Aspiring then to greater things and to a leadership over the Greeks, he attacked first the Achaeans, expecting that, once victorious, he would have allies and especially desiring that they should not hinder his designs.