Found in the behind the main waterfall. Audio puzzle: Match the four-note song Morwen hums using conch shells arranged on a stone altar.

At night (in-game time: 22:00–04:00), you’ll see a faint beneath the waves. Dive from your rowboat (press E near the glow). Swim down 20 meters to find the chapel ruins. Enter through the broken archway.

Keep health items ready at all times and watch your stamina during the final boss fight.