To obtain these Opals, you need to Diablo 4 Items finish the dungeon associated with each Realmwalker. These Opals stack with other elixirs and bonuses, potentially giving you up to a 30% increase in XP when combined with Seasonal Journey bonuses.

How to Start the Realmwalkers Quest
To initiate the Realmwalkers quest, visit the city of Zarbinzet and speak to Crusader Damond. This begins the Creeping Hatred quest, where you’ll defeat a Realmwalker and cheap Diablo IV Items complete a Seething Realm dungeon.