Nice crossover/parody image. I absolutely love Castlevania, and I really like the background of this peice with the castle silhouette in the moonlight, and the creepy hand-like branches of the trees, with red detail outlines along the trees, (looks very reminisc of the famous "Giggle at the Ghosties" scene) and the grass tufts are a nice detail to. The coloring is quite good, and gives it a dark nightime look to it, and looks very true to the FiM show. I also like CT's hat, and carrot weapons.
I also like how you used one of the lesser-known BG ponies, instead of one of the more popular ones.