John I Tzimiskes
In addition to these more or less stable units, any number of shorter-lived tagmata were formed as favoured units of various emperors. Michael II raised the "Tessarakontarioi", a special marine unit, and John I Tzimiskes created a corps called the "Athanatoi" (Gr. Ἀθάνατοι, the "Immortals") after the old Persian unit.