From Hindupedia, the Hindu Encyclopedia
The temple consists of two temples-One dedicated to Lord Shiva facing east and the other dedicated to Goddess Parvathi which is facing west. The peculiarity of this temple is that while Lord Shiva’s temple is open all round the year, the temple of Parvathi is open only for 12 days in a year. There is an interesting story behind this practice.
It seems the Shiva temple was not here but in a place called Iranikkulam near Irinjalakkuda. An old Namboodiri from Srimoola nagaram who was a devotee of the God Shiva used to daily cross the river and walk a long distance to pray to this God. There was a boatman called Chathan, who used to keep a boat and who used to help the Namboodiri to cross the river. Chathan was one among those 12 famous children of Vararuchi about whom the legend of the "Parachi Petta Pandheeru Kulam" is about. When the Namboodiri became very old, one day he cried before Lord Shiva and told him, “Oh God, this is my last visit. I simply cannot come and see you again.”
That day while returning home, the Namboodiri felt that his umbrella was unusually heavy. But as soon as he crossed the river and got down, it became very light. Chathan,, the boat man told the Namboodiri that Lord Shiva had come along with him in the umbrella and as soon as he got down, had occupied some place in the village. Next day, a lady grass cuter, when she was cutting the grass, happened to cut a stone upon which the stone started bleeding.The women was terribly freightened and ran about three kilometers and died out of shock at that place. Chathan told all people that the stone she cut was God Shiva of Iranikkulam. A temple was built there for Lord Shiva and it was called Thiruvairanikkulam. They also built a temple for Goddess Parvathi. The place where the grass cutter fell is today called Varanattumadam. In this place annually a special Pooja called Irukki Pooja is conducted. After the pooja, puffed rice is given as Prasadam. People believe that by taking this puffed rice all diseases would be cured. The stone boat of the Chathan is still preserved in this temple.
Initially, it seems the priest used to keep all ingredients for making the offerings to God (Naivedyam) inside the temple premises of Goddess Parvathi and then close the doors. After some time, the fully cooked Naivedyam was prepared by Goddess Parvathi and kept ready in her temple. One day a devotee peeped through the Window to see what was happening in side the Parvathi temple and he saw that Goddess Parvathi herself was cooking the Naivedyam. The Goddess got very angry after this incident, and asked the priest to close her doors for ever. All the devotees wailed and requested her to pardon the act of the ill conceived devotee. The goddess pardoned him but gave permission for her door to be opened only for 12 days in a year.
Her temple gate opens on the Thiruvadira festival day. A minstrel singer called Brahmani amma sings about the Goddess before her gates are opened.Recently the only member of that family called Sridevi refused to sing at the festival. Thereafter, her husband became terribly sick and the goddess came in her dreams and pointed out that she was insulting the Goddess by not singing. Sridevi realized her mistake and started singing again in the festival. Not only her husband was cured but she was also blessed with divine powers.
Since any body with prayer for marriage or child birth who visit the Goddess Parvathi during those 12 days, gets their prayers fulfilled. Large number of devotees from all parts of Kerala visit the temple during that period.