Chapter One:Call of the Archmage
You can get this quest from Khadgar's Servant in your garrison when you hit 98, follow this quest, you will find Archmage Khadgar in his tower in Zangarra, Talador. Speak to him, he will offer you a quest Spires of the Betrayer which need you to get a quest item: Pure Solium Band from the last boss of Skyreach. Come back to Khadgar, he will give you a level 640 legend ring.
At this moment, chat with Khadgar and he will offer you four quests: three are completed in Heroic Dungeons, Core of Flame need you collect the quest item: Core of Flame which is dropped by Gug'rokk from Bloodmaul Slag Mines Dungeon. Collect Core of Iron from the Engine of the Grimrail Depot train, Grimrail Depot Dungeon. Core of Life, dropped by Yalnu of The Everbloom Dungeon . The last quest is : Draenor's Secret Power requires you get 4968 Apexis Crystals.
After handing those in, Khadgar will hint you to kill Teron'gor in Auchindoun and loot Corrupted Blood of Teron'gor. Talk to Khadgar again, he will upgrade your ring to level 680.

Chapter Two: Empire's Fall
It requires you to kill Ko'ragh and Imperator Mar'gok to get the two quest items Felbreaker's Tome and the Sorcerer King, after handing these 2 items to Khadgar, he will let you collect 125 Abrogator Stone which you can loot from Highmaul bosses. After this, you are sent to speak with Khadgar and locate Gul'dan with his scrying spell. Follow Garona's trail into the Zangarra lowlands. Find, defeat, and capture her. The last thing you do in this part is to speak with Archmage Khadgaragain, he will upgrade your ring to lvl 690.

Chapter III: The Foundry Falls.
In this part, you need to complete 2 quests first. Reverse Piracy and Heart of the Fury. Then you need to collect Flamebender's Tome from Flamebender Ka'graz. At the same time, you can start another quest, Might of the Elemental Lords, which requires you to collect 3 Elemental Tablets. Each Elemental Tablet needs fusing together 300 Elemental Rune. You can collect the Elemental Rune stone from Blackrock Foundry bosses. After handing those in, and complete the rest quests Khadgar offers, he will increases your ring to level 710.