Speak with Swallow at the main hall after the meeting with Peng. Finish the conversation before following the marker to your guest room.

Follow the gold marker to the guest room and enter to rest. After the scene advances the time, investigate the smoke outside.

Head to the work area outside the guest room and speak with Feng and Lei. Their experiment introduces the refining task at the nearby worktable.

Use the worktable beside Feng and Lei. Add sulfur and Beiting Sand in the recipe's displayed ratio, then grind the mixture. Choose Place in Furnace when grinding is complete. Finish the experiment and speak with Feng to continue toward Divinecraft Pavilion.