Speak with Moira at the Stormwind Embassy to travel to the Firelands and empower the Fragment of the Molten Core.
Alright, the hard part should be behind us, <name>.
Now, we just need tae take that Molten Core fragment ye recovered into Firelands an' charge it up by Ragnaros' old swimmin' pool.
Dinna worry! I'm sendin' Anvil-Thane Thurgaden with ye.
Just give me a nudge when ye're ready.