Cosmic Monster: the Apotropaiadon

Something like a reptilian crab.  Instead of claws, a pair of eyeless jaws lunge and snap at the end of its "arms".

Atop its back is a metallic membrane that curls and flexes, like a crown, or perhaps the sail of a dimetrodon.  The flesh of the shoulders blends evenly into the semi-translucent metal of the sail.

Light is reflected off the reflective sail and into a non-Euclidean direction, where its true face is.  This is how it sees.

When it wants to get a better look at its surroundings, it stretches and turns its sail, like a man holding a mirror around a corner.  As it moves, you can glimpse reflections of its real face.

It uses mirrors to copulate with itself*, and then lays its eggs in the same mirrors.  An egg embedded in a mirror appears as an optical distortion that sometimes pulses and crawls, like a lazy maggot.  Note that the egg doesn't bend the mirror or have any mass--it exists only as a bizarre lensing effect.

If the mirror is cracked, it will bleed.  If it is broken, it will disgorge the mangled larva and alert the parent.

This is the first cosmic monster that I've written about that is capable of easily communicating; you may want to brush up on your outsider psychology.

from MightyToy.com

They are often called here in order that they might be coerced into guardianship, hence the name.

Apotropaiadon

HD 5  AC chain  Bite 1d12
Move human  Int 6

Rewind -- Can undo the last 6 seconds (a combat round), at will.  Creatures who are engaged with the apotropaiadon will eventually notice this time-jump, while other creatures won't.

Option: Subtle Rewind -- The apotropaiadon begins combat (or negotiation) already knowing a good chunk about the party's abilities (or disposition), since it has already used this ability a few hundred times before the party noticed, learning by saying provacative things and making bold attacks.

Discussion

Yes, the apotropaiadon can easily stalemate forever.

Yes, the apotropaiadon can easily just reset the combat round until the PCs all have missed their attacks and the apotropaiadon has succeeded on it's attack rolls.

However, you can't just say "the apotropaiadon is going to keep rerolling the combat round until it gets the results that it wants, so let's assume that all of your attacks are critical misses and all of the apotropaiadon's are critical hits", since there is a chance that the apotropaiadon might die from a critical hit on one of the rounds.  If it gets stabbed in the heart, it dies instantaneously, and never has a chance to use its ability.

My party eventually killed it by trapping it in a room with a crush-trap ceiling for six seconds, and then activating the trap.  Since the apotropaiadon couldn't rewind to a time before it was trapped in the room, it couldn't escape through it's rewind ability.

After rewinding time several thousand times and attempting everything it could think of (attacking different parts of the door, trying to jam the mechanism in different ways, pressing every brick in case it was a secret "off" switch) the apotropaiadon gave up, and died cursing the party on the other side of the door.

At this point, the party was not far from giving up themselves, having pulled the same lever a few thousand times.  (At least in the fiction.  The players around the table were like "fuck this guy, my character is going to pull the lever a million times, and talk shit every time".)