If you've seen Alien or any of its sequels. You know what I'm talking about. Instinct: Lay eggs and conquer territory

• Kill people
• Silently attacks from behind cover or behind prey
• Hivemind - each xenomorph is mindlinked with their queen. If they are in trouble, they can telepathically call for assistance from the queen who then sends other xenomorphs to their aid.
• They are older than Man, Elf, or Dwarf
• Acid blood
• Bite at Hand/Close range
• Tail can stab or slash at Close