One of the best ways to build a campaign is to think about the creatures that the players will be fighting. One of the best ways to play in a campaign is to embrace the spirit of the story and make it your own.
To be clear, we’re looking at alien-themed campaigns set in an otherwise familiar fantasy setting for Pathfinder or D&D. The best aliens, however, are those with a look and a feel that’s totally “other”–they have a way of interacting with the world that is totally strange to us. We can’t get inside these creatures’ heads at all. Their very bodies are almost at the limits of our imagination.
Some of these will be Pathfinder, some will be from 3.x. They’re pretty easy to convert to one or the other. We’ll be leaving out monsters that are alien but stupid.
Monsters from the Bestiary
Page 8 in the Bestiary. A classic monster that fits right in with any alien campaign. They’ve got slime, they’ve got a strange mindset with inscrutable plans. They even have an alien slave race and hermaphroditic bodies. These are great for mastermind creatures in an alien campaign, or better yet the overlord creatures that serve even stranger masters. Aboleths fit an “alternate development” kind of alien theme, where a dominant species has developed under aquatic conditions.
Page 35 in the Bestiary. Along with many other oozes, the black pudding is weird and wild, with a totally different “mindset” and way of living than we can begin to understand.
Page 55 in the Bestiary. Not the most interesting monster under most circumstances. However, treat them as a kind of dangerous terrain feature in alien caves and tunnels. Even an infested “spaceship” or two, if your story supports such strange and ancient things, crash-landed before the empires were born.
Page 136 in the Bestiary. It’s called a Froghemoth. No more need be said than this: frogs are sort of the Pathfinder version of what happened with “flying manta ray monster” in 3.x: they’re everywhere! It’s like every time someone was wondering, “where do we get a new monster?” frog-monster was the default idea. Nevertheless, the Froghemoth is pretty cool and distinctly alien.
Page 180 in the Bestiary. A classic brain monster. Alien and weird in every way, although the brain-thing is a bit on the tired side.
Page 249 in the Bestiary. The awesome thing about the shoggoth, besides its weird and wild look, is the “maddening cacophony” attack. It’s a great case of mechanics giving a unique “feel” to a monster. All those weird mouths described when the monster first appears actually do something! What a revelation.
Monsters from Bestiary 2
Page 9 in the Bestiary 2. You’d probably want to rewrite the flavor text on these guys, but their mind-breaking illustration and creepy soul siphoning mechanic make them perfect. Four arms with a galaxy in the middle is one of the most alien monster descriptions ever. Or it’s a swirling eye, if you prefer. A lower-level version is the great Theletos Aeon (page 14 Bestiary 2).
Page 12 in the Bestiary. This is going in a slightly different direction, but the Pleroma has a nice “master of the cosmos” feel, and his mechanics use creation and destruction as forces. A great last implacable enemy if you’re going for the cold otherworldly sense rather than gibbering bughunting.
Page 23 in Bestiary 2. These guys are rare in that they actually are written as being from another planet. A great creepy low-level alien that can be pumped up later and hunts in packs. Be sure to add their eerie silence as they bite and rend and hunt, to better distinguish these guys from howlers.
Page 45 in the Bestiary 2. Rarely an interesting monster, Belkers work best in a multi-dimensional campaign where they can be described as being partly in the 13th dimension. Then they get an eerie feel that will affect players.
Page 54 in the Bestiary 2. They’re mostly interesting for their flesh-warping mechanic. Their appearance is tiresome and pasta-like, but surround them with the fleshy gobs of former humanoids and they become otherworldly and terrifying.
Page 64 in the Bestiary 2. Perfect if you’re building a sound-based alien cosmology. Otherwise not very interesting, unless used as backup to a more vibrant monster.
Page 77 in Bestiary 2. Classic Space Pasta. Don’t pretend it’s anything else. Well-designed without multiple attacks, but you can redesign for a higher-level threat.
Page 83 in Bestiary 2. Works for a sound-attack alien theme, don’t use it otherwise.
Page 85 in Bestiary 2. One of the few demons/devils that actually work as aliens. It’s a creepy and strange beast, perfect for an overlord monster or some kind of galactic senator.
They start page 141 in the Bestiary 2. Wonderful and hilarious monsters that are strange and annoying. Use them to get your players all in a tizzy. As aliens, think of these guys as “infestation” monsters, along with the invasion of something else.
Hound of Tindalos
Page 158 in Bestiary 2. Wonderfully well-designed monster. Works best in a multi-dimensional campaign, and has a special brand of weirdness that’s totally unique. You can use this monster either as the basis of an entire campaign or as a random horror from beyond the stars. It can be a pet, an assassin, a boss, or a mind-screw monster with equal utility. Not to be missed.
Page 195 in Bestiary 2. There are lots of weird “plant things” that could be used in an alien campaign, but the Mu Spore is great because it can be used to make an entire region feel strange and otherworldly. Works as either an invasion monster or local flora/fauna.
Page 229 in Bestiary 2. The 3.x rast would not have made it on here. The Pathfinder rast is weirrd. It can work, but isn’t all that great.
Page 269 in Bestiary 2. Yes! Wacky, weird, and undead. Great if you’re using a lot of fleshaping aliens. It’s freakishly fast and insanely proportioned. A worthy inclusion in many alien campaigns. Use as a terrifying assassin monster.
I didn’t include several monsters that felt like tired repeats. I also didn’t include insectoid alien monsters, as the cast majority of these have boring mechanics as designed. Go your own way if you want those guys, is my advice.