Lord Kubera is the god of wealth and is also known as the "keeper of the treasures of the gods". Goddess Lakshmi creates wealth, and Kubera's work is to distribute wealth. They are also mentioned in Buddhism under the name ‘Jambhala’.
They have been created by God to take care of all the assets in the universe. But initially it was not so, everyone used to make fun of Kubera because of his fat body. Then he did very hard penance to please Lord Shiva. Lord Shiva appeared in front of him and asked which boon he wanted. When Kubera asked for the boon of becoming popular and receiving the respect of all, Lord Shiva made him the protector of all wealth. After which everyone started worshiping Kubera and started chanting Kubera mantras to get the blessings of Lord Kubera.
It is said that if chanting the mantras of Lord Kubera for 3 consecutive months 108 times daily, then he is happy and gives his blessings. On the contrary, it is believed that chanting of these mantras to fulfill the selfish and greedy purpose denies the purpose of the mantra and invites Kubera's wrath.