In The Lord of the Rings, the Nazgul almost found the One Ring a few times in their search. In the Two Towers, one of the most scary moments is when Frodo, Sam, and Gollum are hiding in the ruins of Osgiliath. The Witch King almost uncovers the Hobbits, but Frodo perseveres and they remain hidden. This scene has been recreated by Aaron Newman in this Lego MOC called “Wraiths With Wings!” The build features two main parts. The ruined tower base, and the massive brick-built Fell Beast that can perch on top. The dragon like beast is fully posable, and even features folding brick built wings. The full range of movement in the wings and in the body means that the beast has to be designed very carefully. There needs to be enough support to hold up all the weight, and all that weight needs to be perfectly balanced on two feet (and sometimes a tail). For some added support when perched atop the tower, there are a few technic pins holding it on. According to the designer this ended up being the hardest part of this build. One of the best details is the work done in the head and mouth of the Lego Fell Beast. The bright red tongue and sickeningly pink mouth contrast with the muted colors of the dragon. The end result looks terrifyingly great, it almost looks like it could be an official set. The final model 1,251 pieces, which is a bit less than expected.
You can find a lot more detail (including instructions) about this Lego Fell Beast and Nazgul over here: https://www.aaronbrickdesigner.com/blog/2020/5/13/wraiths-with-wings