Name Source Type X-ists Church of the SubGenius X-Nauts Paper Mario: The Thousand-Year Door X Parasites Metroid Fusion Xandarians Marvel Comics Humanoid Xanthuans DC Comics' Legion of Super-Heroes Xarians Battlelords of the 23rd Century Xarquids X-COM: Terror from the Deep Xchagger Star Control Xeelee Xeelee Sequence novels an enigmatic and supremely powerful Kardashev Type V alien civilization Xel'Naga StarCraft An ancient race that created the Zerg and Protoss. Xenexian Star Trek Xenomorphs Alien movies Parasitic Xenu Scientology Xiangs 2300 AD Xiao Fengqing Legend of Heavenly Tear: Phoenix Warriors Humanoid Xilians Invasion of Astro-Monster and Godzilla: Final Wars Humanoid Xindi Star Trek Humanoid Xorda Sonic the Hedgehog comics Xxcha Twilight Imperium Peaceful arboreal testudinoids Xyrillian Star Trek