Yes they walked the Earth in abundance millions of years ago, and now rarely walk the Earth in present times. In modern times the raising of a Demon from non-corporeal Hell into biological form on Earth is big deal, and requires major mojo. It’s usually kept a big secret because Angels, and other forces of good would swoop in to stop it from happening. It’s said that the Devil himself will translate into a biological form to father the infamous Anti-Christ. Such a summoning ceremony will be the biggest event the forces of evil on Earth have ever seen. These magical ceremonies must be done by evil inhabitants of our physical reality because magical barriers created by Angels exist to keep Demons in the 5th dimension. However this wasn’t always the case, and a fair amount still managed to possess humans on their own. In the far past before humans existed demons ruled over the Earth.
During the Cretaceous Period of the Mesozoic Era some 65 million years ago amid the dinosaur animals a sentient bipedal humanoid reptile being appeared out of the evolutionary soup. They are known as Dinosauroids, and they were in fact the first intelligent species to evolve on Earth thereby making us humans the second. The Devil knew of Gods plans to create humans, and that he was preparing the Earth for their arrival over time so future scientists would see that everything looked natural. God didn’t want any evidence of his creation because he wanted to see what humankind did without his influence. Evolution is actually an intricate program in Gods pure thought matrix mind rather than being a random process. The Devil hacked the evolution program, and caused the evolution of dinosaurs. God chose to ignore the Devils transgression and thought they’d make interesting curiosities. However the Devil hacked Gods matrix again, and inserted an intelligence program causing the creation of the Dinosaur People aka Reptilian People. These Reptilians didn’t have demonic DNA just as humans don’t have Angelic DNA. Although the Reptilians souls were born as demons in hell just as human souls are born as Angels in Heaven. So they were a race of damned souls. In addition to that several Demons, and ArchDemons took direct biological form with complete demonic DNA, and walked among their people as royalty. They blended right in as they looked reptile like as well. The Devil, and his inner circle stayed in Hell keeping a low profile since Angels were after them.
The Devil took great delight, and pride in his intelligent creations boasting that he had created his own race of biological sentients before God. So they existed for thousands of years on super continent Pangaea and the Dino society advanced to a level many hundreds of years beyond ours. They even began to colonize space, and travel to other star systems. They also lived on Mars which was somewhat Earth like at the time but with mostly deserts. The Reptilians naturally followed a Devil based religion, and were devoid of morals. God considered them an abomination on his paradise Earth so he sent an asteroid to Earth that fell as the infamous meteor that wiped out the dinosaurs. A great deal of the Devil’s people along with the biological demons were destroyed as well. Those that survived lived underground since the Earth was a dark dust polluted void. Eventually they all moved to Mars.
Despite Mars being a dying planet God sent forth another meteor killing more Dinsauroids. Eventually they became space nomads who finally settled in the Andromeda Galaxy where God left them alone. They still exist there to this day but a group returned to Earth thousands of years ago with a plan to join human elites in an Armageddon to reclaim the planet for the Devil, and his demons once again. These are the Reptilian Aliens who now walk among us in nefarious league with the secretive Illuminati of the New World Order.