After lighiting Lanka using his tail, Hanuman jumped into the sea in order to cool and refresh himself. A drop of his perspiration fell into the mouth of a great
fish which gave birth to a mighty hero named Makara Dhvaja. Makara
Dhvaja is considered the son of Hanuman.
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Makara dhwaja ? can't recollect the correct .. he is alleged to be son of hanuman.. was a gatekeeper to the fort of mairavana/ahiravana in patal? hanuman had to fight him/defeat him to rescue rama/laxman