The Rajani are a new Neutral faction which features unique rewards such as a mount, a pet, and essences to enhance your Heart of Azeroth. After reaching exalted, players can earn Paragon reputation with the Rajani. Paragon reputation allows players to earn reputation beyond Exalted, rewarding players with Rajani Supplies for every 10,000 reputation afterwards. The cache contains extra Azerite as well as a chance to receive the Jade Defender pet and/or the Roots of Magnificent Revival and Pulsing Star Heart rank 4 essences.
The quartermaster is Zhang Ku who can be found in the Silent Sanctuary at (44.5, 75.4) in the Vale of Eternal Blossoms.
Here you can buy Rajani for EU or US Servers.
Also you'll get guide for completing Rajani
You will be able to obtain unique rewards such as essences. Recipe, pet, tabard
Branch of Rejuvenating Rings Essence
Gleaming Star Shard Essence
Recipe: Contract: Rajani
Troop Requisition: Rajani Sparkcaller Recipe
Lightning-Forged Augment Rune
Windfeather Quill Pet