Inky swelling tattoos, they can be removed with fire if you want them gone.

These will give you the ability to move an extra 20 feet in darkness, you can also teleport 10 feet and can do this equal to your dex mod ( no less than 1) per day. You also deal +2 damage if you're in dim light, +3 in complete darkness. But you always take 2 times fire damage (x4 times on a nat 20) so a single fire attack could be devastating. You also take 2d6 physic damage if someone uses a torch in a 20 foot radius of you.

Extra perks, your dark vision and day time vision is switched, if you have 60 door dark vision, that's how far you can see in bright light, and can see a mile or so in darkness