Sacrificial Altar

Location

Found in Undead Settlement, in the Pit of Hollows bonfire area. Or, if the player has not killed Curse-rotted Greatwood, it can be reached by examining the cage on a Hollow Manservant's back. He is found past the rooftops with the Hollow Slaves.

Usage

It is used to obtain rewards from the Mound-Makers covenant, by offering Vertebra Shackles.

Information here is accurate for version 2.15.