You need to have deathgriper olny my friend... if you need to reach the 2 other tresure chest...
jum in the water at Weeping Crag in front of Gorewood you can see griper point purple colour at celling...
Now from the Locked door with sacrified key seal.. wall ride to right side of the door, step down, go wall ride to right, right again until you reach the POLE, now go up then go to the platform on your left from pole... fight a few enemy until you find dungon map and sacrificed key... then unseal the door and jump into the water continue dive to fight boss to complete side quest... by the the way dont try to fight this boss if your level below 5 or 6... 2 hit all it takes to kill you...