The Warhammer 40,000 Psychic Awakening: Phoenix Rising book contains:

Supplementary rules for Craftworld Eldar and Drukhari armies
Rules for using dedicated Ynnari armies
Supplementary rules for using Ynnari with Craftworld Eldar, Drukhari and Harlequin 8th edition codices
Theatre of War and missions related to the Phoenix Rising story
Updated datasheets for the Triumvirate of Ynnead: Yvraine, Visarch and Yncarne