AaryaPhantomhive: It's Jagua. It's a South American plant that dyes the skin blue/black. It's kinda like henna in that it dyes the upper layer of the skin and it's all natural and safe.
Im testing it out on two spots on my arm. The name and one up my arm that's a flower. When the paste came off it was undetectable, like completely invisible no stain at all. But now its almost black!