Picture of Professor Gray above.
Lucy's second class of the day was Study of Ancient Runes. Lucy took an empty seat and a few moments later, Hermione sat down beside her. Harry and Ron were taking Divination, which took place at the same time as Study of Ancient Runes, so they were nowhere to be seen. Fortunately for Harry and Ron but unfortunately for Lucy and Hermione, Draco had also taken Study of Ancient Runes.
A door, likely adjoining the Professor's study and classroom swung open. The assumed Professor walked to the front of the classroom before facing the class. Lucy couldn't help but notice that he seemed familiar. His eyes roamed the classroom, taking in the number of students and who those students were. When he scanned the students his eyes rested on Lucy for just a few moments more than strictly necessary.
"I am Professor Gray, I will be your Study of Ancient Runes teacher. I expect the respect you should give your other professors. If you have a problem with that I suggest you leave. The door is right behind you if you need assistance finding it. You won't be needing your wands so I don't want to see them out. Put them away."
Just then the large door swung open to reveal Luna.
"Oh...my mistake. It seems I have taken a wrong turn somewhere." Luna found Lucy in the crowd and the two locked eyes. Lucy's eyes flickered from the professor and back to Luna, and rose an eyebrow to give Luna a questioning look. Luna simply nodded and skipped away.
"What a loon." Draco mocked but his laughter was cut short by Professor Gray.
"Mr...Malfoy was it? If you wish to speak you must raise your hand and wait to be called on." Following his reprehend he began his lesson, "Now then..."