- Central Earthen Peak
In the room found to the right of the windmill after climbing up the ladder next to the dart trap.
- Upper Earthen Peak
Found inside of an illusory wall after the Crescent Sickle Phantom and to the right.
- The windmill near the second bonfire can be burned with a Torch. Doing so lowers the amount of poison in the boss room and removes other poison pools around the level and in Harvest Valley.
- A Pharros contraption is in the room filled with breakable poison jars. Activating it creates a water spring if you burned the windmill; if you didn't, it creates a poison spring. The water spring heals poison and restores HP.
- The summon sign of Jester Thomas is located on the right side of the staircase near the two Wardens guarding the entrance to the boss. You will not be able to see his summon sign unless you've burned the windmill.
Starting from The Mines bonfire in Harvest Valley, take a right and you'll come across a canyon filled with poison mist. Kill the Undead Steelworker on the wooden bridge that goes over the poison mist and head straight across. You'll find a doorway that leads into a room with poison pots and two Undead Steelworkers inside. The first Steelworker is immediately left of the door and the second one is on the other side of the room, but they're far enough apart to aggro separately. Let each one come to you so they run into the pots and becomes poisoned for some free damage.
Head straight across the room and you'll end up in Earthen Peak on the main path. Before continuing it is recommended to return to your previous bonfire and rest. You only need to kill three Undead Steelworkers to return to the entrance and the Covetous Demon guards the area's first bonfire, so it's a good idea to heal and recharge before you start.