The Great Revision, as coined by Zaros is said to be the end of the current universe and the beginning of a new one.
At the beginning of each cycle, the Elder Gods 'hatch' from their eggs inside the Elder Halls found on the perfect world from the previous cycle, (currently Gielinor) and crawl to the rift inside and then proceed to suck the Anima of the world dry to nourish themselves. Shortly afterwards, the Elder Gods then proceed to destroy every planet except the one they just hatched on.
It can be deduced that the Elder Gods then spend their time and energy trying to create the next perfect world to produce the maximum amount of Anima so that their offspring can be nourished. However it is believed from Zaros' account that this is not always accomplished and that many Elder Gods died and/or are born stillborn from a lack of sufficient Anima thus making the Elder Gods & the multiverse in danger of ceasing to exist.