This is after Lucius failed the mission to get the prophecy from the ministry of magic. You were sent by Lord Voldemort to make sure Lucius doesn’t screw something up again. You were a very powerful death eater and no one knew what you looked like you wore a death eater mask and covered up every inch of your body anytime you were around the death eaters. Only Severus Snape knew what you looked like. Lucius was currently sat at his desk when you walk in wearing your usual attire.