The Mirror of Erised
Reasoning: The card of wishful fantasies, addiction and lack of control. It can mean that you either need to loosen up and dream a little, or it can mean that you need to stop floating on a cloud of unrealistic wishes and self-indulgence.
The Mirror of Erised shows Harry his greatest impossible fantasy: to be together with his deceased family. It gives Harry a painful feeling of happiness, and he would be content to sit and stare and fantasize all day if he could. But Dumbledore reminds us that "it does not do to dwell on dreams and forget to live", and that people have been driven to insanity by clinging to the illusions shown in the mirror.
In a traditional tarot deck, this is the Seven (7) of Cups.
Notes
I'd always wanted to draw a Mirror of Erised scene. I had a great time with this card. The mirror itself was fun to draw (even though the symmetry was a challenge to do all by hand). The reflection of Harry was a challenge... it was pointed out to me that the back of Harry's head should be a tad larger, to show that he is in a different dimension from those in the mirror.
I hope it's clear enough... I wanted to show Lily's hand on his shoulder, like they did in the movie, but I also wanted Harry directly in the middle and in front of the mirror, so this became a challenge. I made 'real' Harry a bit brighter in color than those reflected, so hopefully that helps.
James and Lily are very similar to how they appear in the Judgment card, outfits included. It was fun to draw them both 'alive', happy and in color, as well as silver, stern 'shadows'.