Once players successfully wake up the Flaming Fist mercenary Art Cullagh in Baldur's Gate 3, and share what they know with the druid Halsin, he'll ask the party to help him retrieve Thaniel, the spirit of the land. The curse set by Ketheric Thorm cast Thaniel into the Shadowfell, and Halsin has a plan to get him back.
Baldur's Gate 3: How To Find And Heal Thaniel
Thaniel is the spirit of the Shadow-Cursed Lands, and healing him is instrumental to restoring the region's former beauty.