Wikipedia
Helmichis ( fl. 572) was a Lombard noble who killed his king, Alboin, in 572 and unsuccessfully attempted to usurp his throne. Alboin's queen, Rosamund, supported or at least did not oppose Helmichis' plan to remove the king, and after the assassination Helmichis married her. The assassination was assisted by Peredeo, the king's chamber-guard, who in some sources becomes the material executer of the murder. Helmichis is first mentioned by the contemporary chronicler Marius of Avenches, but the most detailed account of his endeavours derives from Paul the Deacon's late 8th-century Historia Langobardorum.
The background to the assassination begins when Alboin killed the king of the Gepids in 567 and captured the king's daughter Rosamund. Alboin then led his people into Italy, and by 572 had settled himself in Verona, which made him vulnerable to the ambitions of other prominent Lombards, such as Helmichis, who was Alboin's foster-brother and arms-bearer. After Alboin's death, Helmichis attempted to gain the throne. He married Rosamund to legitimize his position as new king, but immediately faced stiff opposition from his fellow Lombards who suspected Helmichis of conniving with the Byzantines; this hostility eventually focused around the duke of Ticinum Cleph, supporter of an aggressive policy towards the Empire. Rather than going to war, Helmichis, Rosamund and their followers escaped to Ravenna, the capital of Byzantine Italy, where they were received with full honours by the authorities. Once in Ravenna, Rosamund was persuaded by the Byzantine prefect Longinus to kill Helmichis in order to be free to marry him. Rosamund proceeded to poison Helmichis, but the latter, having understood what his wife had done to him, forced her to drink the cup too, so both of them died. After their deaths, Longinus dispatched Helmichis' forces to Constantinople, while the remaining Lombards had already found a new king in Cleph.