Right at the start of your journey to level 120, you will be summoned by Magni Bronzebeard to Silithus to retrieve the Heart of Azeroth. Wearing this necklace you will be able to collect a new type of power: Azerite, 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 Azerite will increase the level of Heart of Azeroth and empower those items, unlocking even more abilities. For more details about how to unlock and empower the Heart of Azeroth check our in-depth Azerite guides:
Azerite Trait UI