When I got to this zone, I must have found like five or six of these on or around King Tormax's throne. Two of them were in the flames of the lanterns around it (very difficult to see). So, they were right next to Tormax who is see-invis, very hostile, and literally impossible to kill. Nice touch! (You can get yourself non-KOS by killing frost giants and apparitions, though.) Seems the last person to collect these didn't bother with this location and allowed them to build up there. Maybe you'll have the same luck. I'd suggest starting there.
Other than that, it seems like these can be kind of anywhere where storm giants congregate (these are the plate-looking giants). Also found some in the frost giant houses that are just north of the second archway (if you're coming in from the Eastern Wastes), so "look everywhere" might be a good strategy for the Kael sets.
Edited, Jun 10th 2018 2:57pm by ShadowsCT