Wrathion asks you to meet him on the Isle of Thunder by the thunder forge after you speak to him in the veiled stair. You speak to him in his whelpling form to start the solo scenario.
In the Scenario you have to defend Wrathion while he charges up the thunder forge, you have some shado-pan guys helping you out. There are a few waves and the last wave has a 10m+ hp mogu.
During this there will be blue lightning balls appearing at certain areas and it is marked with an arrow, you go pick it up and you get a buff that increases your damage and healing.
Once you do this part you get to enter the forge itself where Wrathion summons a celestial blacksmith to start charging the anvils to temper the lance. You have to defend the blacksmith from sha monsters during this and you have a celestial defender helping you out. There are multiple anvils and once each one is charged you can click them to deal aoe damage. There are also green pillars of light that appear which you can stand in to heal.
After all the anvils are charged, Wrathion does a massive aoe and thinks it is over but instead summons a sha boss with 30m+ hp.
The celestial defender is supposed to be the tank while you do damage. The boss has a couple of abilities.
-Main one is Insanity which does massive aoe damage and you HAVE to interrupt it or you die. If you click on one of the charged anvils (they all get recharged if you used them in the first phase) it interrupts the ability so make sure you save them.
-Does a meteor shower which will appear as circles on the ground and will follow you around, just dont get hit.
-Banishes the defender for a short amount of time and you gain aggro, he doesn't hit too hard but if you dont want to risk it just kite.
When the sha boss gets low the lance becomes clickable. Click it and use your special action button to kill the boss and the scenario is done and you receive the lightning lance for the next quest. Good luck!
Hello again, <Name>, was it? Yes yes... I believe we left behind some unfinished business back in the Eastern Kingdoms. How you been finding Pandaria?
I have another assignment for you, if you are up to the challenge this time. I assure you the rewards will be worth it.
Before we begin, it's important that you familiarize yourself with the lay of the land. Come visit me once you have earned more experience here.
It is very good to see you again, <Name>! I trust the weapons I gave you at Ravenholdt have served you well?
I have another "assignment" for you here in Pandaria. This will again require all of your skills, and again I assure you... it will be worth it!
Before we begin, it's important that you familiarize yourself with the lay of the land. Come visit me once you have earned more experience here.
I am glad you have returned <Name>! I trust you are now acclimated to this strange new continent of Pandaria?
You have already proven yourself to me in the past, so we can dispense with any sort of tests or trials. Let's get right to it.
Are you ready to change the world?