I was running from Whiterun to Markarth on a quest and as I approached Windshear pass I noticed two giants crossing the road.As I got closer to the giants I noticed that they started to glow red,and as I got right up on them they did not get defensive and the red glow was coming from their tattoos.Well of course I was curious and followed them, then the red glow stoped for a few moments and started again and then stoped again, so I looked around and noticed that it was a clear night with both moons in full but there were wisps of clouds that were passing infront of the moons and as the clouds cleared the tatoos started to glow again.

This is the first time I encountered this and I have not seen or heard of anything connected to this, does anyone have any theories?

I haven't encountered that yet, but I have encountered a giant in the Eastmarch standing (or what appears to be mourning) over a dead mammoth. He doesn't attack you when you get close either. Can't find anything online about it.

NICE, hope I found something that no one (other than Beth.) has any idea of !!!!! I played for a whole day just to see if it happened again but sadly no. I do belive it's connected to the phases of the moons? I know of the giant youre talken abotu and it does look like he's mourning the loss of his mammoth.