Look for Neloth as you enter Tel Mithryn and when he starts cursing ‘hear stones’ you’ll know it’ll trigger this quest once you speak to him.

Once Neolth has finished casting a spell on you, travel back to Skyrim and go on the hunt for a Forsworn Briarheart . Kill one and then return back to Neloth with its heart.

Briarheart’s Skyrim Locations¶