A talking skull at the Tranquil Halls wants me to tighten the seals on the surrounding tombs. I'll first need to dismantle the skeletons that wander out, then carry their bones to the altar nearby to send their spirits back, and finally seal their tombs shut.
After you kill a wandering skeleton, click on the body to harvest its bones and take them to the altar ( 424, 170, 511 ) Copy/waypoint 423.51, 170.32, 511.25. Click the altar.
Return to the tomb where you slew the skeleton, and click a loose tomb seal on the door for your update.
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