You are looking for WINTERdeep Warren in NidaVellir. Helgrind Warren is also there. One has the tome the other the Crow. To get to them you must go down the ramp under the Rainbow Bridge and enter the tall doors. You'll see 3 sets of sigils. One for each of the Warrens on the left and right side and one for the Hall of Valor which has Jotun in it. You must be finished with the first half of Grizzleheim before you can fight him.
