Living glaciers are found on the high cliffs north of Storm Gorge
Arctic cliff Striders are found past the Rime camps in the far eastern section of Storm Gorge.
NOTE: At around 50% life the CliffStrider and Living Glaciers will split into two or three smaller versions of the main mob, all need to be killed to get the credit. At 1% health, the cliffstrider currently being attacked will no longer take any damage, but it will continue to fight you. Switch target to the second cliffstrider and kill it so that the first cliffstrider can then be finished off. Living Glaciers are similar except they split into 3 at different percentages.