Now that you have your teammate's Soul Heart, it's time to bring them back. To do this, you'll need to find an Altar of Dark And Darker Gold Sacrifice. These altars are scattered throughout the lower levels of dungeons, so be prepared to explore and locate one quickly.
Once you've found an Altar of Sacrifice, follow these steps to complete the resurrection:
Interact with the Altar and select the option to offer the Soul Heart.
Sacrifice a portion of your health—this is required to complete the revival.
Confirm the resurrection, and your teammate will be brought back to life.
However, reviving a fallen ally comes with risks. If you die before reaching the Altar of buy Darker Gold Sacrifice, both you and your teammate will be lost, rendering the effort useless. Additionally, when revived, your teammate won't have any of their Dark and Darker Items, so be prepared to protect them while they regain their strength and gear.