The closest description would best be explained through this image. https://osirisnewdawn.gamepedia.com/media/osirisnewdawn.gamepedia.com/thumb/5/5c/Night_Walker.png/1200px-Night_Walker.png
Its very similar, only it is in some kind of desert, it is extremely big, and it has a simple biological structure. Just four legs in a cross-shape, and a mouth underneath its central torso like an octopus.
What's the movie that shows this monster?