The other person is right. Ancient Egyptians used black crushed lead ore called kohl to paint around their eyes like eyeliner for protection from the direct sunlight that is in Egypt, cause the sun can be very harmful for the eyes and sunglasses were not yet invented. Both guys and girls of all ages did this in ancient Egypt... so that's probably why the auteur did that.
The egyptians also wore eyeliner to look pretty... no, I'm being serious. Both the guys and the girls were very vain and cared greatly about their looks, and they thought eyeliner made them look pretty... lol.
I vote for best answer.......even though I already knew about the first half. Football players do the same when they put black stickers under their eyes. I say stickers because I dont think that most use paint anymore...
Well the egyptian eyeliner thing is a good answer but what about the fact that they were underground all dag every dag until the pharoh return so there is not really any sun for them to be protected from. My guess would be either a tattoo a scar of a birthmark cause his dad had the same kind of markings too.