You sit down in the dark of the lonely night with your own pumpkin in front of you. You close your eyes and try your best to imagine what your own special Shadow Cat would look like as you light the candle. You watch the tiny ember burn brightly for just a minute or two, before you close your eyes and blow out the candle.
Don't forget to make a wish when you blow out the candle (any certain traits you want):
This is hard... so I'll give you a prompt instead: "A beast of blue fire, or ice, who dwells in the shadows." Go wild. If I had to choose one trait, though, an elemental extra or bioluminescence would be cool - or multicolored smoke. You're under no obligation to use those traits.