You have to enter the Nyctocosm dimension, Find the lava biome with obsidian ground ( forgot the name ) and then you have to use your ring in offhand with the Sorcerer Sword in main hand then do shift and right click, it will create a circle and then in the middle, throw a Wither Rose and the teleportation will begin, just stand in the circle to get teleported correctly and then enjoy the boss fight
this is epic
How to go fight the cataclysmic emissary
You have to enter the Nyctocosm dimension, Find the lava biome with obsidian ground ( forgot the name ) and then you have to use your ring in offhand with the Sorcerer Sword in main hand then do shift and right click, it will create a circle and then in the middle, throw a Wither Rose and the teleportation will begin, just stand in the circle to get teleported correctly and then enjoy the boss fight