As it was theorized in the first release of NPCs, space creatures could be found. As this was not implemented yet, I thought that I should start a suggestion thread of possible monsters. I would love to find out what everyone else wants to see when it is implemented. Also, I would think it would be interesting if organic modules could equip up to 10 but all of them count to this limit.

As for my own ideas:
Tachyon Eater: An obstruction to many space goers looking for new planets, these bloated creatures absorb tachyons from the surrounding space for nourishment. Normally docile, they become aggressive around large sources of tachyons (such as those found in many ship sensors).
Traits: no shield, medium attack and medium defense, a massive hull, 1 player
Special ability: engorge tachyons (gives penalty to ship scanning)
Artifact: void organ (bonus cloaking for 1 week)

Phase Spider: Crafty predators, they have ambushed many ships by staying out of phase until the last moment before their attack. From their frail features, they rely on spinning a web of phase energy to take the blunt of most attacks. Many trade caravans have fallen victim to their insatiable apatite.
Traits: high shield, low hull, medium defense, high attack, 1 player
Special Ability: Ambush (gains bonus to attack for 2 hours after the first round of combat)
Modules: Phase Web Shield (max shield), Phase Venom Launcher (attack), Phase Spider Hide (cloaking)

Elder Space Dragon: The stuff of legends, the space dragon has only been documented by the lucky few who managed to make it to escape pods before the ship was vaporized. Highly territorial with a hunger for dysillon and kurenite, only the brave (and foolish) have ever attempted to take down an elder. Lucky you.
Traits: high attack, high defense, high shield, high hull, strong everything. Made for 12 players.
Special Abilities: Disruptor Breath (gives penalty to attack, defense, scan and cloak for 1 day), Temporal Dissonance (gives +1 truce for 1 day), Quantum Anomaly (damages your most expensive ship module [if many are the same, it chooses randomly])
Modules: Dragon Heart Reactor (max energy), Dragon's Breath (attack), Dragon Scale Armor (hull), Dragon's Aura (shield)
Artifacts: Elder Wisdom (gives a lot of research), Anomaly Bomb (offensive artifact: disables opponent's most expensive module)
Buildings: Dragon Bones. Show the galaxy that you are a force not to be trifled with! (huge bonus to invasion defense, size 1, limit 1 per planet, can only be awarded to the player who first shared the NPC)

Hm, I like this idea! Not only could you battle monsters, but you could also get some cool organic modules. More could be added over time. I actually thought of my own

Space Squid/Kraken
A large Kraken like monster with powerful crushing tentacles. Normally this life form eats rocky asteroids, but starship hulls often offer more exotic flavors, and they will attack to protect their young. Their skin is tough, and covered with bony armor plates. They are hard to defeat, but their heads are vulnerable.
Special Ability-Entanglement-Your ship is covered in tentacles...-15% to defense
Module Rewards-Kraken Skin-Hull and Cloak --Kraken Tentacles-Weapon adds attack and small defense value
Artifact Rewards-Sucker Sphere-A blob of suckers off of the tentacles, it takes out a large part of defense, and shield strength.

Fralo...

Your squid/Kraken... --> Artifact: Energy SYPHON! That's what them little suckers should do!! Drains energy from target and transfers to cores for storage.

~Drake

...Ah. That's actually not that bad an idea. I like that one better. Here's another monsters

Plasma Creature
Entities that are simply spheres of plasma. They are not violent, unless you pester them. Incredibly intelligent, they often only attack ships if you attack them. They're plasmic nature makes them difficult to kill, and only higher level weapon like Graviton shearers will really harm them. Plasma weapons also have no effect on them. If you arrange for it, you can hire some to help you in your exploits.

Artifact Rewards-Plasma Wave Trap-A powerful blast of plasma that can easily destroy enemy ships. Deals a large amount of damage
Module Rewards-Plasma Creature Brigade-A small legion of plasma creatures that have been hired by you. They take up little space, and have large up keep but increase shield and attack strength.

The Nightmare Beast
Second only in lore to the space dragon, this entity is your worst nightmare...literally. This creature is very aggressive, and normally resembles a large black cloud. Get too close to the cloud, and it transforms into a hideous monster that attacks your ship. Infusing the crew with fear, terror, rage, and cowardice, and feeds off of their reaction. Nobody has ever really defeated it, and little knowledge is gained from probes, because it only attacks ships with lifeforms aboard. One thing is for certain...it can only be hurt when it attacks you, when your crew is under the greatest sensation of fear, and imagining their worst nightmares coming to life. If you can overcome that...and fire upon the creature, it's insane power can be used to your command...

Abilities-Worst Nightmare-Creates a sense of incredibly fear in your crew. Decreases attack and defense.
Artifact Rewards-Nightmare Bomb-A burst of psionic energy that causes the enemy ship's crew to go insane. Instantly disables a ship.
Module Rewards-Nightmare Beast Brain-The brain of the creature has been salvaged and given cybernetic implants to keep it under control. This ultra-computer spreads it's neurons throughout the ship and can make the ship much like the beast's gaseous form...or in the minds of your enemies, their worst nightmare. Increases everything but energy.

Yeah, it's creepy, but it's cool.

a problem with the void organ is this, if it disables scanning to everyone else why wouldn't it disable the cloaking of the person who used it? if it provides you with cloaking then it should disable your scanning somewhat.

Like most cloaking devices, it reduces incoming radiation and particles that most ships use to scan, much like the radar-absorbent paint on a real-life stealth fighter, and stealth fighters don't have any trouble using their own radar.

The silthion are supposed to be rapidly evolving space creatures, so I would guess any of these could really fit under that umbrella if they had to. -1 to space dragon. I will cry if this game becomes DnD in space. I think the paladin/knight/dragon/ranger legion names provide more than enough of that as it is.

The space krakken sounds pretty cool though. Maybe something that drains your energy as long as it is in your battle tab. These NPCs have been completely passive from the get go.

I actually got the idea of a space dragon and phase spider from Pardus.

And another monster:

Asteroid Creeper: A large worm-like creature that dissolves minerals found in asteroid fields for sustenance. As a self defense mechanism, it will flood its surroundings with its corrosive gel whenever something approaches it. It is advised to let professionals remove it as its gel sacs will rupture if it is killed.
Traits: no shield, average hull, average defense, high attack
Special Abilities: Corrosive Field (deals moderate damage every hour it is on your battle tab), Corrosive Detonation (deals massive damage to the player that disables it)
Buildings: Domesticated Creeper (size 2, +3 mining, max 1 per planet)
Artifacts: Corrosive Mine Trap (1 week ship trap, deals 100 damage to opponent's ship every half hour for 5 hours)