Here is a creature I created for a Mystara campaign I ran a while back. The PC's, who started at first level, began to rise into the ranks of the movers and shakers in the world.
Although these creatures are quite deadly, I designed them to be more than a combat encounter. The Skellar they met became a recurring NPC, one that they came to regret associating with. They tend to be subtle.
Armour Class -8
Hit Dice 22+20******* (120 minimum)
Move 180' (60')
Flying 360' (120')
Attacks 2 claws, 1 tail + special
Damage 3d6+8 / 3d6+8 / 3d6+6
No. Appearing 1 (1)
Save As Fighter 25
Treasure Type Special
Alignment Chaotic (Neutral/Evil)
XP Value 18,500
Originating from another planet, the Skellar are completely alien creatures whose motives and goals are unknown. They are humanoid, usually standing seven feet tall, but often move on all fours to confuse others about their size. Their skin is dark grey and looks like a suit of tight fitting full plate made of leather, a sort of semi-chitinous exoskeleton. They have no face; only a smooth egg-like surface. They do have a mouth, though, one filled with wicked metallic teeth. Protruding from the back of it's head are pencil thick hair-like stalks that drape down two feet over it's shoulders. Emerging from it's back is a huge set of bat wings that span up to twenty five feet. They also have a long, bony tail that ends in a sharp chitinous blade.
Despite it's lack of eyes or ears, the Skellar has excellent senses. Unless sleeping, which it only does for 8 hours per month, it can never be surprised. It can always detect invisible creatures or illusions and can see into both the Ethereal and Astral planes.
In combat, the Skellar use all their abilities to their best. They use their claws as a Master (Weapon Mastery), doing the indicated damage above, and gaining all the to hit bonuses. If they succeed in hitting one opponent with both claws, they will pull them in and bite them with their immensely powerful jaws, which they can unhinge, like a snake, automatically hitting and doing 3d6, plus the targets Armour Class. The bite of a Skellar is poisonous; those bitten must save versus poison at - -2 or die. If they succeed, they still take an additional 20 points of damage.
A Skellar's tail is used less accurately than their claws; they hit at the normal chance for their Hit Dice.
Any creature of less than 4 HD who comes within 20 feet of a Skellar will flee in terror for 1-10 rounds. All others must save versus Paralysis or also flee.
All Skellar are accomplished spell casters. They cast spells as a 14th level Magic-User. Their spells should be carefully chosen. They usually have a number of spells per level in their books equal to twice the number of spells they can cast per day.
Because of their alien origin, the Skellar have a personal Anti-Magic of 35%. In addition, they are immune to electricity damage and take half damage from fire and cold attacks and they can only be hit by weapons of +2 or better.
In addition to all this, a Skellar can use each of the following abilities as often as desired, once per round, in place of any other action, as a 16th level caster: Hold Person, Know Alignment, Cause Disease (reverse of Cure Disease), Dispel Magic, Charm Person, Phantasmal Force, Teleport any Object, Death Spell.
Despite their alignment, not all Skellar are truly evil. All are thoroughly alien, though. Their goals are often things that would seem lame to others. There was once a story of a Skellar who joined a party of adventures on their journeys, requiring only that they pay it daily in the form of dry rations. More often than not, though, they will happily kill those who get in there way.
Skellar rarely collect treasure. On occasion, they will acquire magic items, which they will always use, if possible.