I was asked this morning if angels can die. Angels are holy and live in the Kingdom of Heaven. They have the LORD'S protection. How can angels who never knew any sin, die; with the exception of Lucifer and the fallen angels? The angel in Daniel 10:13 did not die but was rescued by the archangel Michael. The LORD sent support. He backs up His angels in Battle. There is no way GOD would allow and angel to perish at the hands of the evil one. Daniel 10:13 just means there's a reason why sometimes the answers to our prayers are delayed. Do not be deceived by the enemy by wasting time contemplating nonsense this nonsense. GOD'S angels are HOLY. What can kill HOLINESS? NOTHING! Evil has no power over holiness. I once asked the LORD about angels and He said He takes them from Strength, to Strength, to Strength, to Strength. They only get stronger. That angel battled 21 days with the kings of Persia and may have won the battle but it may have just taken longer to do it and the LORD may have wanted Daniel's prayer answered sooner than that particular angel would have delivered His message so the LORD send reinforcements (Michael the Archangel) to help that angel out. The Bible does not say that the angel lost the battle. The angel said that he was withstood by the prince of Persia 21 days and that he had remained there (fighting) with the kings of Persia (Daniel 10:13). That angel was battling more than just one entity.
"But the prince of the kingdom of Persia withstood me one and twenty
days: but, lo, Michael, one of the chief princes, came to help me; and
I remained there with the kings of Persia" (Daniel 10:13, KJV).
'Kings' is plural. That was one good fight that angel put up alone to battle 21 day. NOTE also, Scripture states, 21 days, not almost 21 days as mentioned above in the comment. Note this scripture states not only did the Michael the chief of princes come to help this angel but this angel still remained there. Hence, this angel "DID NOT DIE."
"The evil will bow before the good, And the wicked at the gates of the
righteous" (Proverbs 14:19).