Rowan's Tattoo was a magical tattoo covering most of the body of Rowan Grey. It allowed her to expend charges in order to suck the life essence from her enemies, and heal herself in the process. It also allowed her to attack someone who attacks her!
The tattoo (or tattoos) appeared in the shape of roses, flowers, and thorns, and it wasn't in black and white, it was gold and red and green. It glowed slightly, and would glow a little brighter when she used its power. It crept up her neck, but didn't appear on her face, other than, on either side of her face, a small strand came up to her ears.
As a reward for defeating Lucious Incendous in Bone Fire 42, The Tower of Grey was allowed entry into The Elite Forge, which housed a number of powerful and magical weapons. Rowan was given the Blood Fury Tattoo as a gift. It appeared as a 6 inch long needle, dark red, with handle of darker red encrusted with rubies and gold. She pressed the needle against her forarm, and it began to melt away, dissolving into the very ink of the tattoo. In essence, the needle became the tattoo.
The tattoo had 10 charges Rowan could use, all charges regained daily at dawn.
She could expend a charge when she hits a creature with a weapon attack to deal an additional 4d6 Necrotic damage, and gain those Hit Points for herself.
She could also expend a charge whenever someone hits her with a weapon attack, and make a melee attack against them, with advantage.