Question: How Demigods Can Be Mortals?
You have stated that the demigods are mortals like us. How can you confirm this when there is so much difference between the demigods and ourselves? How can you say that they are in the same category as ordinary humans?
Answer: They Die When the Universe is Destroyed
The answer is very simple. When the powerful demon Hiranyakasipu petitioned the chief demigod Lord Brahma for the boon of immortality Brahmaji told him, "Since I am not immortal, I cannot give you immortality." The demigods are powerful controllers of this material universe. That's a fact. But at the end of Brahma's life this material universe is destroyed along with all of its inhabitants, including Lord Brahma and the thirty three million demigods. Therefore Lord Krishna states in the Bhagavad-gita that demigod worship is for those who have lost their intelligence. If we worship the demigods, we go to the demigods and remain mortal. If we would like to become immortal, we can do that by worshipping Lord Krishna, the source of eternal existence.