Viswara is the son of Creator Brhamma and the daughter of Tiruvanavindhu. Kubera is the son of Viswara. Ravana is the son of his step-mother. The original king of Lanka was Kubera. Ravana later usurped the Lanka kingdom from Kubera. The aircraft of Kubera, the Pushpaka would be spilling precious stones at all places while in flight. It is said that Ravana had to face problems only after the exit of Kubera.
Kubera was a staunch Shiva devotee. Pleased with his penance, Lord Shiva along with Mother Parvathi graced His darshan. Seeing Parvathi, Kubera felt that he had not worshipped so beautiful a Goodess like Parvathi when one of his eyes beat softly and stopped. Exasperated Parvathi caused his eye burst. Kubera lost an eye. When he begged the mother to pardon, She graciously did so but said that the vision would not be restored. Yet Lord Shiva replaced it with a small eye. He also lauded his penance and appointed him as the head of the Northern direction. Lakshmidevi appointed him as the custodian of food grains. It should be understood that Kubera is not the owner of wealth and food grains but only a custodian. His job is to ensure their security. Giver is Mother Lakshmi.
“Ohm, Yakshaya Kuberaya Vaisravanaya, Dhana Dhanyathi Pathaye Dhana Dhanya Samruddhime, Dehi Thapaya Swahah” is the Kubera mantra chanted by devotees seeking the grace of Kubera.