There was a great Asura named Bali, incapable of being killed by any crcature. Assuming the form of a dwarf, you exiled him from the three worlds.
अवध्यः सर्वभूतानां बलिश्चापि महासुरः। वामनं वपुराश्रित्य त्रैलोक्याद् भ्रंशितस्त्वया॥