That Green Fellow

Find the Green Fellow: Head to the statue in the plaza. You'll trigger a cutscene that dives a bit deeper into the whole Stormterror situation. Turns out, this guy is actually a bard named Venti. He'll recognize the crystal you have – Dvalin's tear – and notice that the impurities are gone. He's got one too, and he'll ask if you can do the same for his. Just hold the tear in your hand, and poof, the impurities vanish, just like the first one. Venti will mention that Dvalin is suffering from his own rage, even if he's not defeated. Then, he'll tell you he's heading to the 'Symbol of Mondstadt’s Hero' and leave. After this scene, the quest wraps up.