Stewart eventually deduced that the Guardians had the energy to send the cities home whenever they wanted, and that they let them remain on Oa as an experiment in cosmic integration, and also as a test for John Stewart. Stewart passed the test, and discovered that he was a figure in Oan prophecy. That was why the Guardians directly chose him instead of allowing a Power Ring to do it, as is standard procedure. John Stewart rose to a new level of awareness and became the first mortal Guardian of the Universe. He was also rewarded with the resurrection of Katma Tui, which caused him to break up with Rose.