Despite not being able to unleash the full power of the Infinity Stones until the very end of Avengers: Infinity War, Thanos made good use of the gems he did have throughout the rest of the movie. On Titan, he battled Iron Man, Spider-Man, Doctor Strange, Star-Lord, Drax, Mantis, and Nebula, and the villain was able to overpower all of them.
During the course of that fight, Thanos used the Stones to transform some boulders Iron Man had dropped on him into bats, which he then sent flying at the Armoured Avenger.
It was a brief moment, and we never really got to see those creatures in any detail. Thanks to concept artist Jerad S. Marantz, though, we now get to see just how much work went into creating them. They're undeniably terrifying, and it's definitely a shame they didn't get a little more screentime in the movie.
"Had to do a couple revisions to this guy," the artist explains, "and was surprised to see how you couldn’t really see them in the film, but that happens a lot. Originally these [creatures] were going to be much more prominently featured." Ultimately, it seems Marvel Studios and the Russo Brothers felt they didn't need to have a particularly significant role.
Check out the Avengers: Infinity War concept art below: