Ratnabhishekamurti is a form of Vishnu or Sri Krishna. In this form, Sri Krishna avatar of Bhagavan Vishnu sits under the Kalpavriksha tree. The leaves of the tree shed gems and other precious stones. As Sri Krishna sits under the tree the gems falls on him and thus abhishekam is performed with gems and precious stones to Vishnu.
Kalpavriksha is the wish fulfilling tree in Hinduism. The tree is believed to have appeared during the samudra manthan or churning of ocean. Indra, the king of Devas, took it to Devaloka and planted it there.
Ratnabhishekamurti is worshipped for wealth and money. It is believed that this form of Sri Krishna blesses a devotee with prosperity. This form also worshipped to overcome all kinds of financial problems.
There is a belief that this form blesses an unwavering devotee with sudden wealth – like winning lottery or winning games etc.