Developed as I've gone through my CULT OF UNDEATH project, and just a bit of my ISLES OF TERROR project too (although I may yet have more from that) here's some more monsters that can be added to your FANTASY HACK game.
HEADLESS HORSEMAN: AC: 16 HD: 4d6 (16 hp) AT: touch +4 (1d6) STR: -4, DEX: +2, MND: +1 S: undead immunities, only hit by magic or silver weapons, arrows do a max 1 HP damage. Also: drains 1d3 DEX on touch, creatures reduced to -5 DEX are immobile and helpless for coup de grace attack that kills them automatically, forces a Sanity check on all characters that can see the horseman.
MOUNT: AC: 15 HD: 5d6 (20 hp) AT: bite +5 (1d6) STR: +3, DEX: -1, MND: -3, S: breathe fire (1d10 HP damage—DEX + Athletics check DC 14 will halve damage.)These two go together, needless to say, although it would be unusual that the mount would continue to fight if the horseman was killed. Headless horsemen are often geographically bound; i.e., if you make it out of the woods that it haunts and crosses the covered bridge that leads to town, you have escaped from it. Or something along those lines.
GHOUL-HOUNDS: AC: 13 HD: 2d6 (8 hp) AT: bite +2 (1d6) STR: +2, DEX: +0, MND: -1, S: touch paralyzes for 1d4 rounds, humans wounded by ghoul-hounds are cursed if they fail a MND + level check (DC 12) and will slowly turn into ghouls themselves. This process involves taking 1 point of MND damage every day (which does not heal overnight) until they reach -5, at which point the conversion is complete. GM may provide antidote/remedy to counter this curse.Ghouls hounds are to wolves or large dogs what ghouls are to people; a kind of undead monstrosity with many of the traits of a ghoul. These horrible canine monsters sometimes haunt the area surrounding a powerful undead, such as the forest around the castle of a vampire lord.
SPIDER-BABOON: AC: 12 HD: 2d6 (8 hp) AT: bite +2 (1d6) STR: +1, DEX: +3, MND: -4, S: Acrobatics affinity, successful bite attacks deliver poison. Target must succeed on STR+Level check DC 14 or take 1d4 STR damage. One minute later, a second check must be passed or character takes 1d4 DEX damage.A monster that was supposedly bred in Hell; these are like an agile primate, but with multiple eyes like a spider, and a poisonous bite. They are not native to anywhere on Earth, but may infest certain cursed areas, and some powerful sorcerers even summon one as a familiar (since it has 2 HD, any sorcerer of 4th level or higher.)
NIZREKH ROYAL HERESIARCH: AC: 17 HD: 10d6 (40 hp) AT: touch +5 (1d6) STR: +4, DEX: +2, MND: +3, S: undead immunities, only takes half damage from non-silver weapons, regenerate 3 hp per round, on a successful hit (MND + level to resist, DC 19) does 1d4 STR damage, can hypnotize (MND + level check, DC 19), avoids crosses and mirrors, immobilized and apparently dead if a stake is driven through its heart, cause fear in creatures under 4th level/HD, can cast spells up to 5th level.While the vampires of Timischburg have a powerful undead grip on immortality (of a sort) they are pale shadows of the true masters of undeath, the Royal Nizrekh Heresiarchs. There are only a handful such that exist, but all are powerful scions of undeath and thaumaturgy, and attack with powerful physical as well as magical abilities when they are spurred to combat. They rather spend their time in Machiavellian manipulation against each other and other rivals, however—if they are reduced to fighting for their lives, usually something has gone really wrong for them.
Like Liches, Heresiarchs have horcruxes that make their total destruction extremely difficult, and many enemies that think that they have destroyed one find to their fatal chagrin that they just keep coming back.
The best literary comparison to the Heresiarchs is the Ten Who Were Taken from Glen Cook's The Black Company.
SPIDER, GIANT: AC: 15 HD: 7d8 (35 hp) AT: bite +6 (1d6+4 plus poison) STR: +6, DEX: +1, MND: -4, S: successful bite attacks deliver poison. Target must succeed on STR+Level check DC 14 or take 1d4 STR damage. One minute later, a second check must be passed or character takes 1d4 DEX damage.Modified from wyvern stats. Less of a Shelob and more of the Mirkwood spiders, though.
DOPPLEGANGER: AC: 14 HD: 3d6 (12 hp) AT: broadsword +3 (1d6), STR: +2, DEX: +2, MND: +2 S: Can change form as a single action.Can mimic the appearance of any character, PC or NPC.
FLESH HOUND: AC: 14 HD: 2d12 (10 hp) AT: bite +4 (1d6+2) STR: +3, DEX: -2 MND: -3 S: Immune to most forms of magical attack. Regular weapons do only half damage. Fire (magical or mundane) does 2x damage.
CHILD GOLEM: AC: 14 HD: 2d12 (15 hp) AT: slam +5 (2d4+2) STR: +3, DEX: -2 MND: -3 S: Immune to most forms of magical attack. Regular weapons do only half damage. Fire (magical or mundane) does 2x damage.Two minor alterations to the flesh golem stats, for a hound-like golem (instead of humanoid) and for one made from the corpses of children.
SLENDERMAN: AC: 16 HD: 4d6 (16) AT: touch +4 (1d6) STR: -4, DEX: +2, MND: +1 S: undead immunities, only hit by silver or magical weapons, arrows do a max of 1 HP damage, forces Sanity check on all who see him, drains 1d3 DEX each round on touch attack. Characters with -5 DEX are helpless and immobile, and will be killed by coup de grace.
MOURNING MAIDEN: AC: 16 HD: 4d6 (16) AT: touch +4 (1d6) STR: -4, DEX: +2, MND: +1 S: undead immunities, only hit by silver or magical weapons, arrows do a max of 1 HP damage, casts Glance of the Gorgon as a 5th level caster once per round.
SNAKEMAN: AC: 16, HD 2d8 (10 hp) AT: bite +3 (1d8+4) or bow and arrow +2 (1d6+4). STR: +2, DEX: +0, MND: -1 S: amphibious, successful bite attacks deliver poison. Target must succeed on STR+Level check DC 14 or take 1d4 STR damage. One minute later, a second check must be passed or character takes 1d4 DEX damage.Powerful children of Medusa (the original) they often are ruled by a lesser medusa (as shown in the stats for FANTASY HACK). They lack the petrification ability, but are quite large and strong, and have a poisonous bite. From the waist down, they are a slithering snake, like medusae, but they lack the snake "hair" and in general have a more serpent-like face.
SNAKE GOLEM: AC: 20, HD 4d12 (28 hp) AT: glaive +6 (2d8+6). STR: +6, DEX: +0, MND: -1 S: Turn to Stone on failed DC 12 MND + level check) if you look the snake golem in the eyeIn the very early days of humanity, when the Heresiarchs of Nizrekh were new, their wars with the snakemen were legendary. Some of their slain enemies were turned into a horrifying creature; undead skeletons of the largest and most powerful snakemen; like giants compared to their stunted cousins who survive today. Their skeletons are fossilized into black marble, but with a baleful light in their eyes, they still serve their conquerors. They also have a bit of the curse of their Mother, Medusa, in that they can turn opponents to stone (albeit not as reliably as the medusae can.)