Sentinel’s Gaze is located in the Maw, close to the entrance to Phariseer’s Tomb.
Enter Sentinels Gaze and continue down the spiral staircase until you reach the break. Wallrun to the pole on the left wall, slide down and wall run back to the left to find a chest. Grab it and return to the pole, wall run across to the right and continue to the bottom of the stairs. Enter the door here.
Follow the bridge to the east and clear out all the skeletons lurking around at ground level here. On the northeastern side of this room you will find a Boatman’s Coin . Return to the central structure and look to the right of the curved face at the front to find a handhold. Climb here and follow the platforming section around until you reach a balcony with some yellow crystals. Enter soul splitter mode.
Return to normal mode and climb to the top. Look at the giant statue to the west to see a crystal. Shoot that for a Stone of Power . Have a look opposite to see a room again guarded by yellow crystals. Enter soul splitter mode once more and send clone 1 down to the bomb plant again and have him stand in the same corner as previously. With clone 2 look to the left of the crystal blocked doorway to see a hole in a wall and a slope of debris leading down. Stand on the very corner of the building closest to clone 1 and use death grip to grab the bomb and pull it up. Detonate the crystals and exit soul splitter.
Enter the room and grab the chest. Drop down the hole behind it to enter Boneriven.