Lay graham crackers out on a rimmed cookie sheet so they're touching each other, about four to each row. You can fill in the empty space by breaking the crackers, if you'd like.

Melt green candy melts in the microwave, stir until smooth, then drizzle over the graham crackers. Do the same for the purple candy melts, and finish with the orange candy melts.

Immediately sprinkle with candy eyes, chocolate candies and Halloween sprinkles. Place the cookie sheet in the fridge just until the candy melts have fully set. Remove and let it come to room temperature, then use a butter knife to carefully break it into large pieces. Place the pieces in mini cauldrons for serving.