Hanuman’s Son Makar Dhwaja was born to a mighty fish of the same name when Hanuman after burning the entire Lanka with his tail had dipped in the sea to cool off his body. It is said that his sweat was swallowed by the fish and thus was Makar Dhwaja conceived. The fish was caught by Ravana’s step brother Ahiravana who ruled Patal, the nether world. When Makar Dhwaja grew up, Ahiravana was impressed by his strength and virility. He then made him his soldier.
During Rams’s quest to free Sita from the clutches of Ravana it was Hanuman who flew across the sea to reach the demons king’s palace and discovered the whereabouts of Sita. When Ravan became aware of Hanuman’s presence in his palace, he ordered his soldiers to capture and kill the petty monkey. In order to crush Ravan’s ego, Hanuman set about destroying Lanka with his tail that was set ablaze by Ravan’s soldiers. In this commotion he found Lord Shani imprisoned in the palace’s basement, who was cursed by Brahma to remain in captivity till an incarnation of Shiva frees him. Hanuman released him from the confinement. Delighted, Lord Shani helped Hanuman in his pursuit to destroy Lanka and even granted him a boon. Hanuman who always wished well for his followers, asked Lord Shani not to cause trouble for the devotees who worshiped Hanuman.