Nandaka is the holy sword of Lord Vishnu, and he is the king among the swords. Lord Vishnu can be seen in some pictures holding the divine sword Nandaka in his arms.
The sword is considered as the companion of Lord Vishnu, contains shining appearance, and glitters like the Dhruva Star.The great Vaishnavite saints Annamacharya and Pey Azhwar are believed to be the incarnations of Lord Nandaka.
The Nandaka sword contains great powers, since he forms part of Lord Vishnu. Through the Nandaka sword, Lord Vishnu had killed the demons Madhu and Kaitabha.
Lord Rama used this Nandaka sword during the time of his fight with Ravana in the Lanka war. During the period of Nara and Narayana, when they meditate in the Naimisaranya forest, they would also keep the Nandaka sword along with them. Once when the great Demon King Bhakta Prahlada had seen the two divine sages keeping the Nandaka sword with them, he got angry and began to fight with them. The fight lasted for one month, and finally when Prahlad came to know about the greatness of Nara and Narayana, he bowed before them, and asked them to apologise him.
Nandaka sword was used by Lord Indra also during the battles with the demons. According to legend, Lord Krishna used this Nandaka sword during his fight with the powerful demon Narakasura.
It is also told, that the forthcoming Kalki Avatar would be using this sword to kill the evil ones in order to protect the good ones. Since Nandaka dwells with Lord Vishnu, he contains the features of Lord Vishnu, and worshipping Lord Nandaka is similar to worshipping Lord Vishnu.
Let the divine weapon Lord Nandaka kill our bad habits, and let him makes us into pure and pious.
“OM SRI NANDAKAYA NAMAHA”