歷史
其人數恰好保持為10000人不變，任何戰死、重傷或重病的士兵都會立即被一名新的成員取代，以此維持部隊的人數與士氣，因此得名為“不死軍”。
波斯阿契美尼德王朝軍隊的核心。被翻譯為“長生軍”、“不死軍”等。
在《斯巴達300勇士》里說他們來自波斯古老的傳說，他們是來自幽冥的戰士，專門獵殺人類的靈魂，殺不死也打不敗。500年來他們替波斯王乾盡壞事，眼睛像夜晚一般黑，滿嘴都是尖牙，沒有靈魂，是薛西斯王的錦衣衛，波斯軍隊的精英，可以說是全亞洲最致命的軍隊。影片中不死軍戴有可怕的面具，當一位斯巴達戰士砍下不死軍中一人面具時，其面容十分可怖。
歌曲
歌手：Marnie Stern
歌詞：
Immortals - Marnie Stern
I'll come and find you
I'll come and find you
I'll come and find you
I'll come and find you
I'll come and find you
All the gods hang around where you are
Open mouths beg for them
How bizarre
Oh the strange
It launched a thousand realms of wings
And what's dangerous
It turned to other things
Immortals don't die
Immortals don't die
Immortals don't die
Immortals don't die
I'll come and find you
I'll come and find you
I'll come and find you
I'll come and find you
All my hero's bold ideas
Well they have gone
Broken up and split into a thousand songs
Their shapes could make it clearest
Who I'd want to be
And the dangerous
It turned to other things
Immortals don't die
Immortals don't die
Immortals don't die
Immortals don't die
Only I could save her
Only I could save her
