From publisher blurb:
“We Come in Peace”?
Martians are extraterrestrials who have decided to invade other planets. Not all Martians are alike: within you’ll discover the militaristic big-brained encephalons, the little green men known as Extraterrestrial Biological Entities (EBEs), the psychic insects known as ataiens, the cephalopod-like sarmeks and their terrifying tripods, and the four-armed tharke warriors. Their vehicles and insect minions are also included for 24 total foes to terrify your world!
Martians are fond of communicating intentionally incorrect information with other species, claiming that they come in peace only to blow them up as soon as their guard is down. Don’t believe them!
This PDF has a bookmarked table of contents, with monsters linked by challenge rating. Challenge ratings range from 1 to 22.