From the site of grace, head down the stairs, and look out for the gargoyle imp around the corner to the right. Continue straight and you’ll see an opening into a larger area — there’s yet another enemy hiding around the corner on the right. Once it’s dealt with, you can go and pull the nearby lever. Then walk down the stairs and turn around; the wall next to the staircase is an illusory wall that you can attack or roll into to dissipate.
Head through the illusory wall and there will be a patrolling gargoyle imp — turn him into rubble and then turn left to grab the Ghost Glovewort . On the opposite wall is a corpse holding a Rune Arc. From the corpse, turn right and head down the passage south, and look left — you’ll see a narrow opening that you can head through. Continue down the stairs to find the corpse holding x3 Root Resin, and then roll into the wall behind the corpse to reveal yet another hidden passageway.
Continue down the stairs, turning left to go down the next flight. Naturally, there’s another false dead-end and yet another illusory wall! Beyond this false wall, you’ll find the door you opened at the beginning of the dungeon. Through the golden fog beyond lies one of the cutest bosses in the game — the Spirit-Caller Snail.
Once you defeat the boss, you can take the wisp back to the beginning of the dungeon, or if you really don’t want to kill the two imps at the start, you can run back to the room with the lever. Either way, from the room just below the lever, continue down the next set of stairs and take out the imp at the bottom who’s likely flinging knives at you. Then turn around and find the next illusory wall, which is in the same spot as the first one (to the right of the stairs).
A gargoyle imp will attack you as soon as you break the wall, so roll backwards once you destroy the illusion. There’s another imp inside the room on the right; once he’s down, grab the crafting materials and the Watchdog’s Staff and x5 Human Bone Shard from the corpses in the corner.
Leave the secret room and go straight, then down the next set of stairs. Stop at the bottom of the stairs and note the trap on the floor, next to where the hall has a T-junction. To the left of the trap is a small alcove where an imp gargoyle will jump down. Avoid the trap and enter the alcove, then take out the imp as soon as he drops down. Then leave the alcove and go left down the hall again. The next area is free of enemies, and you can proceed east around the large center column to find an alcove containing yet another illusory wall.
In the next room, there’s an imp standing in the middle of it, and two more imps hiding on either side of the entrance. If you approach the middle imp, you can pull him towards you without triggering the fellas on either side of the door. Then take out the guys on the sides (they don’t seem to aggro, so you can take them out one at a time) and proceed to the altar to grab the Raya Lucaria Soldier Ashes. With that done, you can open your map and teleport to the dungeon entrance.