Demādes in Harpers Dictionary of Classical Antiquities
（Δημάδης). An Athenian orator, who belonged to the Macedonian party, and was a bitter enemy of Demosthenes. He was put to death by Antipater in B.C. 318. Demades was a man without principle, but a vigorous and brilliant orator, always speaking extemporaneously, and with such freshness and force as to rival Demosthenes himself. A long fragment of an oration (Περὶ Δωδεκαετίας) bears the name of Demades, but is probably spurious.
Demades in Wikipedia
Demades (Δημάδης, c. 380 - 318 BC) was an Athenian orator and demagogue.
He was born into a poor family of ancient Paeania and was employed at one time as a common sailor, but he rose partly by his eloquence and partly by his unscrupulous character to a prominent position at Athens. He espoused the cause of Philip II of Macedon in the war against Olynthus, and was thus brought into bitter and life-long enmity with Demosthenes, whom he at first supported.
He fought against the Macedonians in the Battle of Chaeroneia, and was taken prisoner. Having made a favorable impression upon Philip, he was released together with his fellow-captives, and was instrumental in bringing about a treaty of peace between Macedonia and Athens.
He continued to be a favorite of Alexander, and, prompted by a bribe, saved Demosthenes and the other obnoxious Athenian orators from his vengeance. It was also chiefly owing to him that Alexander, after the destruction of Thebes, treated Athens so leniently.
His conduct in supporting the Macedonian cause, yet receiving any bribes that were offered by the opposite party, caused him to be heavily fined more than once; and he was finally deprived of his civil rights. He was reinstated (322) on the approach of Antipater, to whom he was sent as ambassador. Before setting out he persuaded the citizens to pass sentence of death upon Demosthenes and his followers, who had fled from Athens. The result of his embassy was the conclusion of a peace greatly to the disadvantage of the Athenians.
In 318 (or earlier), having been detected in an intrigue with Perdiccas, Antipater's opponent, he was put to death by Antipater at Pella, when entrusted with another mission by the Athenians. Demades was avaricious and unscrupulous; but he was a highly gifted and practised orator. According to Arrian, Demades was killed by Cassander, Antipater's son,after suffering the slaughtering of his child in his hands. Cassander justified his actions by accusing Demades that he had slandered Antipater in his letters to Perdiccas.
A fragment of a speech, bearing his name, in which he defends his conduct, is to be found in C Müller's Oratores Attici, ii. 438, but its genuineness is exceedingly doubtful.