The Lair of the Fleshrender is a lair hidden in an area of Kadrin Valley, in the RvR lake, due west of Gromril Juction. It is hidden within the western mountains, above the train tunnel. When you discover the area, you will get a Tome of Knowledge unlock.
Approximate Location: 3.2k x 32k
Opening the Lair
To open the lair, one must use three valves starting from the one being down the hill. First Steam Valve is located at 8838, 33629 ; second valve is at 4494, 34903 and the third valve is at 3895, 32731 on the right of the lair's door. Once all valves have been turned on (in order), the door will open.