The Blaze
The Blaze is a massive wall of Chaos energy that encircles the core-fragment of the plane of Varys and is slowly moving inwards towards the Heart of Chaos. As it moves, the Blaze seems to 'burn' the structure out of the plane, leaving behind a constantly shifting world of pure Chaos - not unlike the Wild Sea itself.
Although there is little reliable information about the secondary fragments of Varys, it is believed that each of them is surrounded by a similar phenomena and that they are likewise being slowly destroyed. These fragments are tied to the core of Varys by the Golden Chains created by the Karithkaia, and it is possible, though extremely dangerous, to cross the Blaze by travelling on or near these chains - so moving from the core to the connected fragments and back again.
The last journeys of that type known to be successful were many centuries ago however, and with the Blaze now stronger than ever, it is unclear how practical such a journey would be in modern times.