Gigaschadel as a spectral sort of monster. They appear as giant leering heads, drifting with a sort of dread purpose, like old men sent on errands they care not for but cannot shirk from. Their skin is a waxy gray color, like a corpse, and they all have bleached white hair. They have deep resonant voices, and constantly mumble to themselves, ranting like those afore mentioned old men, caught in a long queue and left to shout about what they did in the war, and being forced to stand in line for milk or a pint. The strangest part is that they are always familiar looking, like they wear the face of someone you've met before, a distant cousin, a lost father.
The Giant Skulls
Gigaschadel are spectral undead and appear as wizened blue grey heads. They are incorporeal and have the same general set of abilities as other ghosts. They can pass through solid materials, are unharmed by mundane weapons, and are immune to illusions, and other magics based around deception. They can be harmed by magic, be turned by clerics as if they were strong undead, and can be driven back with holy symbols but only by the strong of heart.
If you catch it's attention, it will follow you, muttering and mumbling curses to itself and at you. It's eyes bulge and you can see a spectral sort of ooze dripping from their mouths. If you can't fight it, can't drive it away, it will push you in a corner and continue it's dread liturgy until you lose your mind, and are left a white headed simpleton. Those who can offer token resistance are attacked with spectral teeth. The bite deals injuries that leave blue grey bruises, and injure the soul. Those who succumb to these gnawings rise from the dead as restless dead. Empty shells, they wander looking for something to fill them, and that's usually hot screaming human flesh. Those who are equipped and well versed in fighting the undead will find that the gigaschadel can emit a terrible wail that saps the will of those who would fight it, can call forth lesser ghosts to fight on their behalf, and can breathe out a gout of ghostflame.
The muttering and black poetry of the Gigaschadel is a draining effect. Each round constitutes an attack, and failing a saving throw, the victim will lose a point of intelligence or wisdom, whichever is higher. Once both attributes reach zero, the gigaschadel is sated and wanders off. The victim recovers both attributes at a rate of one point per week (assuming a 3-18 score range) until they reach 50% of their previous level, and there is no further recovery. This can lead to loss of spellcasting abilities, or attributes required for various classes.
The bite of the gigaschadel inflicts moderate damage, and bypasses all non-magical armors. If a character is slain, within 24 hours their corpse will rise, still blackened and bruised from the bites, as a low level zombie. They are non-infectious, and cannot create other zombies, but can and do carry horrific mundane diseases.
Summoned ghosts are low level and can be easily dispatched by well equipped PCs. The ghosts function as a distraction, forcing players to spread their attacks and prevent them from ganging up on the gigaschadel. Summoned ghosts inflict cold damage, and given a supply of fresh corpses, can enter them and raise them functionally as zombies.
Ghostflame is a powerful attack, and a Gigaschadel can only do it three times in a day. The gout of flame is a fairly narrow cone of moderate length, but splits into three smaller ghostflame orbs that will track towards the nearest living creature but only have one turn to find a target. Their range is short, 20 feet or so.
Origins of the Gigaschadel
There are no wild/feral gigaschadel. This spectral skull is created through potent necromancy and is a moderate level necromantic spell. Creating a Gigaschadel requires an unholy altar, ceremonial equipment, and a bitter and cruel old man. The spirit of the old man is bound into a spectral form and left to become even more hateful and senile. The ritual is long, as the potential gigaschadel has to spend at least a year 'aging' in a special urn. After this time, it becomes bound to the necromancer that created it, and retains it's intelligence and speaking ability, but only with the necromancer who made it. Everything else is seen through a very warped and damaged lens. The world around the gigaschadel is a miserable hateful place and it's constant dialog is the bitter musings of a ghost lost in it's own thoughts, trapped in a magical cage.
This spells summons a free or rogue gigaschadel, a creature that occurs when it's creator perishes, or they release the ghost to it's own mischief. For it to work, the necromancer must know that there is one in the area that can be summoned, or must know the mortal name of the victim who was turned into the monster, or be a specialized ghost summoning necromancer.
Random Encounter - The gigaschadel is a mid-boss or elite foe in the hierarchy of undead and can be found where there are ghosts, it's origins less important than the danger it presents and the XP it offers.
Demi-Boss - a particularly sentient gigaschadel can taunt and torment the PCs, working as a spectral lieutenant to a more powerful undead or necromancer. As an elite gigaschadel, it can speak with hateful intelligence, cast low level ghostly spells (summon ghosts, spectral sound, ennervate, etc) and make a horrific nuisance of itself. For a recurring encounted, the gigaschadel can (a unique ability) possess a living body so that it can move around and cause more problems for the living. The PCs kill the guy after them, the gigaschadel moves on to inhabit a new body and begin hunting them again.
Grandpa NO! - The gigaschadel is young, but horrifies the PCs as it was created from a curmudgeonly old man that they knew, perhaps a wizened wizard, a gruff bartender, or the disagreeable shopkeep. They know the past identity of the monster, and recognize fragments of it's litanies. How well can they fight a ghost that they knew? Who made it, and was this just a coincidence, or is a necromancer hunting down their associates and turning them into monsters to attack them?