Once brothers Ravan, Vibhishan and Kumbhakaran were asked for a boon they wanted by Brahma. Indra, on the other hand, was jealous of Kumbhakaran’s wit and valour and thought that Kumbhakaran would ask for Indra’s Indrasan – the Kingdom of Heavens. Fearing this, Indra requested Goddess Saraswati to tie Kumbhakaran’s tongue, compelling him to ask for eternal Nindrasan. Brahma granted Kumbhakaran the boon of eternal sleep.
Seeing this, Ravan requested Brahma to undo this as it was really a curse. Brahma did undo it, but he decided that Kumbhakaran would sleep for half a year and then wake up the rest of the year – during which he ate eternally. During the Battle of Lanka, Kumbhakaran was asleep and was walked over by a thousand elephant as that was the only way he could have woken up!