Put a heart in the Ancient Altar in BG3 to open the secret passage in Balthazar’s room at Moonrise Towers. The altar is part of a small puzzle, and the reliable answer is the heart from the nearby viscera/body piles rather than random items or body parts you might be tempted to try.

Quick Scoop

  • What to put in it: A heart.
  • Where it is: Balthazar’s room in Moonrise Towers , behind the bookshelves.
  • What it does: Opens a secret passage to the hidden room.

How it works

You’ll need to reveal the altar first by interacting with the bookshelves in Balthazar’s room, then place the heart into it. That action unlocks the passage and lets you continue the area’s progression.

Note

Some guides mention other body parts, but the most consistent solution reported is the heart.

If you want, I can also give you the exact step-by-step path to find the altar in Moonrise Towers.