Right at the start of your journey to level 120, you will be summoned by 麦格尼·铜须 to Silithus to retrieve the 艾泽拉斯之心. Wearing this necklace you will be able to collect a new type of power: 艾泽里特, the Blood of Azeroth.
The necklace allows you to empower your helm, shoulders and chest pieces, called Azerite Armor, unlocking new exciting powers hidden within those items. Collecting 艾泽里特 will increase the level of 艾泽拉斯之心 and empower those items, unlocking even more abilities. For more details about how to unlock and empower the 艾泽拉斯之心 check our in-depth Azerite guides:
Azerite Trait UI