Molten Hills is a huge new continent located on a island, north east of Molten Hills. In Molten Hills you can find mostly end-game monsters.
Molten Hills has a few new features, like lava fishing with a new custom obsidian rod and enchanting items with special stats. Also there is a dungeon available in the Molten Hills.
You can travel to Molten Hills from Cormaya. However, to get access you will first need to start the questline at Donald McRonald in Thais.