Leo 23 was called Leo the Assyrian (Λέων ὁ Ἀσσύριος), Ps.-Symeon 678; Ἀσυλαίων, Georg. Mon. Cont. 830, 837, 839, Ps.-Symeon 685, 688; Ἀσυλέων, Leo Gramm. 253. A nephew (ὁ ἐξάδελφος) of Basilios 7 (the future emperor Basil I), he went on the expedition against Crete in 866 and was involved with Basilios 7 in the plot to kill the Kaisar Bardas (Bardas 5) at Kepoi in Thrakesion: Ps.-Symeon 678, Georg. Mon. Cont. 830. He later conspired with Basilios 7 to murder the emperor Michael III (Michael 11), on 23 September 867; he was among those who kept watch outside the imperial bedchamber when the first attack was made; later, since Michael 11 was still alive, he went in and struck the fatal blows with his sword: Georg. Mon. Cont. 837, Ps.-Symeon 685. This act is attributed to Ioannes 89 the Chaldee in Leo Grammaticus. Subsequently Leo 23 was sent from Constantinople by Basilios 7 to live on an estate of his called Chartophylax, where, because he was excessively harsh and cruel towards his slaves, they murdered him one night; for this the emperor (Basil 7) had them cruelly put to death: Leo Gramm. 253, Georg. Mon. Cont. 839, Ps.-Symeon 688. See Winkelmann, Quellenstudien, pp. 87-89, 91.

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