Makardhwaja / Magardhwaja as per Hindu Religion, is a son of Hanuman, who makes his appearance in the epic Valmiki Ramayana.
When Hanuman took a dip in the waters of the sea (after burning down the whole of Lanka with his inflamed tail), a drop of his perspiration fell into the mouth of a mighty fish. Out of this, Makardhwaja was born.
According to another, slightly different version, when Hanuman took a dip in the sea, to cool himself after burning Lanka; a drop of his sweat got discharged, due to the extreme heat generated in his body and labor by him, and which then fell into the mouth of a giant fish-cum-reptile like creature, whose name was Makardhwaja, thus impregnating it..
The fish was caught by people of Ahiravana, who ruled Patala, the nether-world. The Markardhwaja, was discovered, when the stomach of the fish was cut open and thus he was named after it. Ahiravana, seeing his strength & virility gave him job of guarding, the gates of his Kingdom.
Makardhwaja name is derived from Hindu religious texts' creature Makara and depicted as part Makarā and part Vanarā (monkey).
Makardhwaja is sometimes also spelled as Magar-dhwaja - depicted as part Magarā (crocodile) and part Vanarā.
According to Ramayana told by Valmiki, this story has no place in it. However, in local folk tales this story is related. When Ahiravana took Rama and Lakshmana to Patala, Hanuman followed them to their rescue. He was challenged at the gate of Patala by a creature, who was part Vanara and part reptile - a Makara. He introduced himself Makaradhwaja and son of Hanuman, the mighty warrior.
Hanuman was amused and said that, I am myself the Hanuman but he could not be his son, as he was celibate since birth. However, Hanuman then closed his eyes in dhyana to see the events described above of Makardhwaja's birth.
Makardhwaja asked him for his blessings, however, he said to Hanuman, that he will have to fight him to enter Patala, as he cannot betray Ahiravana, his mentor. Hanuman defeats Makaradhwaja in a duel and binds him to proceed further to ultimately kill Ahiravana and rescue Rama & Lakshamana.
Later on, upon Rama's advice he installed Makardhwaja, as King of Patala before returning to Lanka, to continue war with Ravana.
The Jethwa clan of Kshatriyas claim their descent from Makardhwaja. As per folk tales of their clan, Makardhwaja had a son named Mod-dhwaja and he had a son named Jethi-dhwaja. Jethwas claim descant from Jethi-dhwaja and worship Hanuman as their Iṣṭa-devatā. The Jethwa dynasty of Gujarat, who once ruled major part of Kathiawar and later the princely state of Porbandar, therefore, had the image of Hanuman on their Royal flag.
Temples dedicated to Makardhwaja can be found in India, especially in Gujarat, where Jethwas once ruled. Some noted temples in Gujarat are atOdadar village near Porbandar.
Hanuman-Dandi at Bet Dwarka, where idols of Makardhwaja and Hanuman are worshiped together.
Chinchawan, Tq. Wadwani Wadwani, Dist.Beed (Maharashtra)
In Rajasthan, also there is temple known asBalaji Makardhwaja Temple at Beawar, which is dedicated to both father-son duo in form of Balaji Hanuman and Makardhwaja.