You hid your tattoos because it resembled some very, strong and powerful dark magic, you used some foundation to cover them up so no one knew about them, until at the Yule ball, you started to realize the foundation was wearing off and was showing your marks. You quickly ran out of there without raising any suspicion. You looked for your foundation but you had run out. You turned around and saw your enemy, Snape looking at your marks "You have.." He looked at you frantically