Step 1 — Start
Talk to Goldian, Master of Divine Arts, and accept the quest. He tells you the ancient Valkyria have chosen you for a sacred mission: defeat the raid boss Death Lord Shax, a fallen warrior who has defied the natural order, and prove yourself worthy of the Valkyria's blessing.
Step 2 — Death Lord Shax
Find and defeat the raid boss Death Lord Shax (level 75). Like any raid boss, you can check its current spawn/alive status and location from the in-game Raid Boss Info panel. The moment you land the kill, the quest completes automatically and rewards you with 1x Sacred Tome - Blessing of Valkyria — no need to walk back to any NPC.
Use the Sacred Tome from your inventory to learn Blessing of Valkyria, a passive skill. This is the only way to acquire it.