I completely understand YOS Bricks‘ fascination with the black brick, having been featured myself on TBB before for this reason. You can see the appeal in his build of a Thestral from Harry Potter and the Order of the Phoenix, which uses the black elements to capture the creature’s eerie silhouette.
Again, in a more complex form such as this giant horned dung beetle, the dark colour allows individual bricks to read together as single forms — the insect’s antenna and wings being particularly good at showing this.
Black also works marvellously against brighter colours. The turquoise eyes of the Mooncalf from Fantastic Beasts and Where to Find Them, glow magically in YOS Bricks’ final example.