In Act II, as the player travels through the Sewers, they'll come to a room with toxic barrels and a few noxious Walkers, as well as a Floater. There will be a ladder in the middle which they should climb up and follow the path around to the Purple Skull, which rests in front of a shrine. The shrine contains a picture of a woman and her daughter. It should be noted that the player passes through the location a few times during the campaign.
In Act II while in the city of Moresby, there is a side quest available on the east side of the map called "Uninvited Guests". Once upstairs inside the apartment, the player should head into the kitchen and place the Purple Skull on top of the stove.
In game versions prior to Patch 1.3, after the player completes the quest and leaves the house, reentry is not possible, so the Purple Skull must be obtained before leaving. It was possible to re-enter the apartment if the player had not talked to Alicia Jacobs, thereby completing the quest. As of Patch 1.3, the player can return to the altar at any time. However, there is a bug that will still deny the player re-entry.
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