Shlokam:
Red in color (sin^dhUram), Three eyed, shoulders like yugas (four shouldered), with hands holding up thesUlam , noose, axe in hands, with frightening teeth, nice face, with the left foot standing up over the chest ofkAla (time – death), with cast down red matted hair, to that pashupati(Lord of creatures), kAlAn^taka I prostrate.
Purana of the deity:
kAla ari : The enemy of kALa(vIra mUrti)
kAla is the dEva who is responsible for death. Taking the kAla as time it can be said kAlari represents the fact that God is beyond the limits of time (mR^ityuJNjayan).
The sage mR^ikaNDu did not have an offspring for quite a long time. He performed tapas to get the blessings of Lord shiva. God appeared in front of him. Now the sage had two choices – either a son indiscipline, cruel and dumb living for long or a son loving, intelligent and a gem of character living very short span of life. The sage chose the second one. His wife gave birth to a child mArkaNDEya, out of a boon from Lord Shiva, by which mArkaNDEya would be very intelligent but would live just for 16 years.
Young child mArkaNDEya grew up learning the great scriptures, caring and loving, devotional towards God. His parents were very pleased with him. When he became 16, he found his parents weeping. He came to know that he would die at 16 and that was the cause of the gloom. Intelligent mArkanDeya realized that none other than the God, Who is beyond all the scopes of time and hailed as mR^ityuNJjaya – who conquered the death, can save him from the strong clutches of death. Determined and devotional, he started doing Shiva pUja and surrendered himself completely to the Lord. The yamadUtAs who came to take his life away were scared away by the flame of this young boy’s devotion. As the the attendants couldn’t take away his life, kAla the god of death, himself came. Young mArkaNDEya did not loose his devotion even in the crisis moment. He embraced the shiva liN^gam. As kAla still tried to take away mArkaNDEya‘s life, the Lord appeared furious from the ShivaliN^gam and kicked kAla to death!! He blessed the sincere devotion of the young boy and made mArkaNDEya to be in 16 always – deathless !
All the gods pleaded to Lord to show mercy on kAla. On their request, God gave kAla life back and ordered him not to disturb His devotees.
thiruk kadavUr is the temple associated with this valorous deed of Lord Shiva. 
thirukadavur kAlasamhAramUrthy
Courtesy: www.shaivam.org