Harry Potter Tom Riddles Diary With Invisible Ink Pen & UV Wand Harry Potter Tom Riddle’s Diary Notebook, Slytherin House Pen, & UV Wand. Use as a normal notebook but the Slytherin House pen included is filled with invisible ink which can only be seen under the glowing wand’s UV light. This ensures its magical properties are true to the movie. All you have to do is hover the tip over the pages and what you have written will be magically revealed! Beautiful leather bound effect with aged metal protective corners. Depth: 15 MM Height: 210 MM Width: 135 MM