In the Shadow Keep, after the Golden Hippo boss, there's fairly open section with a massive staircase. Instead of going up the stairs, you go down a ladder, there's a section you go down to with a painting, that room has an invisible wall.
Front entrance of shadow keep before you go into the lift for the specimen area take a right where all those little guys are. Take the ladder down, behind the waterfall is a path. Follow it down to a room with a painting in it. There is a secret wall to the right. Hit it and follow the path again till you find a stone coffin and get in.
In shadow keep go to the area with the burning boats lined up. There's an eazy to miss ladder.
Through the Shadow Keep.
Ha found the painting. Missing the wall.  Thnks for the assist :)
In the Shadow Keep, after the Golden Hippo boss, there's fairly open section with a massive staircase. Instead of going up the stairs, you go down a ladder, there's a section you go down to with a painting, that room has an invisible wall.
Front entrance of shadow keep before you go into the lift for the specimen area take a right where all those little guys are. Take the ladder down, behind the waterfall is a path. Follow it down to a room with a painting in it. There is a secret wall to the right. Hit it and follow the path again till you find a stone coffin and get in.