The Treasure Chest on Shipwreck Beach.
Treasure Chests are buried treasure found throughout Legend of Grimrock II. Unlike Secrets, nothing in the terrain suggests their existence, but various papers and signs offer hints toward finding them. After determining where one is located, it can be dug up by facing the tile it's on and using a Shovel. Unearthing 3 of them earns the Booty Addict achievement, and unearthing all 11 of them earns the Treasure Hunter achievement. It is possible that these chests may be Mimics.
Shipwreck Beach[]
At the lone oak, in the shadow of the blue light, I buried it. - Captain Kilhagan
The hint toward this chest is found in the same map: a Note located in the chest holding a Shovel and the Rapier. The treasure is one tile north of the tree, so that it is between the treasure and the Crystal of Life. No Lock Picks are needed; the chest contains the Embalmer's Robe and a Healing Potion.
Twigroot Forest[]
AR E. UHU KO. AR E. UHU E.
The first chest is hinted at by a sign in the west of the map, though its meaning may be unclear when first read. It gives the directions "Left 1. Forward 3. Left 1. Forward 1." and indicates the corner two tiles west and five tiles north of the sign. Lock Picks are needed; the chest contains a Gold Key, a Shield Potion, and a Steel Armband.
I had more equipment than I could carry so I buried some of it right between the two lanterns in eastern Twigroot Forest.
The Note hinting toward this chest is found in the Twigroot Tunnels, in a Sack along with the Compass, in the northwestern room where an ambush of Undead Soldiers waits. It indicates a tile in the northeast of the map, exactly between the two lanterns near the exit to the Forgotten River. This chest requires Lock Picks to open; it contains the Tome of Leadership.
Forgotten River[]
The clue toward this chest is a Map found in the chest in Herder's Den. The space it indicates is on the eastern bank of Forgotten River, near the Courtyard. No Lock Picks are needed; the chest contains Cheese, Reed Sabatons, and 3 Shurikens.
Keelbreach Bog[]
Underneath
From the clue, a sign found inside a pit in the middle of Keelbreach Bog, finding this treasure is straightforward: dig up the tile directly in front of the sign. This chest requires Lock Picks to open; it contains a Crystal Shard of Recharging and a Torch.
A treasure chest long lost, guarded by the four fallen spirits in the bog.
The hint toward this chest is a Note found in Sleet Island, along with the Tribal Shield on an island northwest of the Shrine of Water. The four fallen spirits it refers to are four destroyed Stone Philosophers in a square near the northwest Power Gem; the treasure is on the tile exactly between the four. No Lock Picks are needed; the chest contains a Crystal Shard of Recharging, a Horned Fruit, and the Thraelm Tribal Buckler.
Sleet Island[]
A Map found in the Tomb Underground, in the northwest chamber, is the clue to this treasure. It indicates a space just east of the entrance to the Ruins of Desarune, on the water's edge. No Lock Picks are needed; the chest contains a Shield Potion and a Zarchton Harpoon.
Cemetery[]
Three steps x and x south from x x
x x west x four x x Cemetery entrance
The clue to this treasure is broken across two Scrolls found in the Tomb of Rites: the first is in a hidden room in the southwest by the Archmage's Scapular, and the second is found in a Secret at the level's entrance. Put together, the Scrolls give directions from the sealed Cemetery door, leading to a small nook with destructible branches, with the treasure underneath. This chest requires Lock Picks; it contains the Bracelet of Tirin and 5 Cannon Balls.
BETWEEN HAARO ERHEP
A very oblique puzzle leads to the second of the Cemetery's treasures. Three of the graves are marked as belonging to the Riddles—Jakon, Ronar, and Miriel. The capitalized letters on each grave's epitaph spell out the respective word, indicating the space between the graves of Haaro the Scribe and Erhep the Master Carpenter. This chest requires Lock Picks to open; it contains a Gold Key, a Letter from Jakon Riddle, and the Rites of the Moon.
Hamlet of Stormbreach[]
There is a fountain with an ancient oak by its side.
From the oak, take four steps to the east.
And then two steps to the south shall you stride.
The treasure now lies beneath your feet.
The Note offering directions to this treasure is found with a Skull in the Cemetery, in a pit in the northeast. The fountain it refers to is one in the Hamlet of Stormbreach, near the center of the map. Following the directions leads to a space immediately south of some stone tiles. This chest requires Lock Picks to open; it contains a Crystal Shard of Protection and the Jeweled Scepter of Ruling.
Barren Desert[]
Where there is nowhere to hide from sunlight, the loneliest of all trees resides.
The missing limb will point you to the right direction.
Just walk as far as the eye can see.
The Note leading to this treasure is found in the Wormbound Catacombs, in an alcove with a Shovel. It refers to the Barren Desert, which has a lone tree in the northeast. A hollow in the tree faces westward; move west in line with the tree and dig up the tile against the wall. This chest requires Lock Picks to open; it contains a Potion of Dexterity, a Potion of Resurrection, and the Silver Scepter of Isochronos.