Arctaris's page

You could have a tiny undead based roughly off of the smoke haunt (i.e. with similiar fire based abilities) and give it the fiendish template. Give it a few constant spell-like abilities (Confusion maybe?) and make it minorly intelligent. Then, make it so that it isn't meaning harm to its victims and doesn't understand its own destructive capabilities. Perhaps its only seeking warmth and companionship but in trying to get close to people it kills them witha fire aura or something similiar. That would make it even more tragic and memorable, perhaps even bringing a something of a moral quandry (Do we kill an obviously deadly yet pathetic, pitiable and helpless creature for seeking warmth and companionship?).
On an somewhat related note, if you're just looking for a sidequest and want something similiar to this, try using Tanethia Wheen's ghost. In the Sandpoint detail in Burnt Offerings its mentioned that Tanethia Wheen drowned several years ago. It also mentions that all of the mills except for the Scarnetti's burned down. With a minor altering of the timeline (I think that the two events occurred a few years apart.) it could be made so that she witnessed some Scarzni thugs burning a mill under the Scarnetti's orders and they drowned her to silence her. I used this and had her rise as a ghost, causing problems in a burnt out mill just trying to get attention and help from the people that didn't know she was there. She really meant no harm and was just trying to get help. The PCs managed to talk to her and she was put to rest after her parents came and said goodbye and her murderers were brought to justice. I started a whole campaign with this and made them do a lot of traveling, but it could easily be truncated to be a side quest.
My two coppers, hope they helped.

Here is a rough draft of the PrC. If it seems a little under- or overpowered let me know and I'll tweak it.

The Runecaster
Prerequisites: Spell Focus (Evocation)
Decipher Script 8 Ranks, Spellcraft 5 Ranks,
Knowledge (Arcana) 3 Ranks
Must be able to cast at least 2 spells with a
runic component.
Hit Dice: d4
Class Skills: Concentration, Decipher Script, Forgery,
Knowledge (Arcana), Spellcraft, Use magic Device
Skill Points per Level: 2+Int modifier

The Runecaster
Base
Attack
Bonus Saves Special Abilities
Fort Ref Will
+0 +2 +0 +2 Runic Weapon 1/day, Runecast,
Runic Specialization, 2 Runes
known
+1 +3 +0 +3 Runecast, Runic Knowledge,
Suppress Rune 1/day, +1 caster level
+2 +3 +1 +3 Runic Weapon 2/day, Runecast,
4 runes known
+3 +4 +1 +4 Runecast, Runic Knowledge, Suppress
Rune 2/day, +1 caster level
+3 +4 +1 +4 Runecast, Runic Weapon 3/day,
6 runes known

Runic Specialization: You cast all spells with a runic component at +1 caster level for all level related effects.

Runic Weapon: To a maximum of three times per day you can lose a spell slot or a spell prepared to scribe a rune on a weapon. This weapon gives the weapon an enhancement bonus equal to the level of the spell slot given up. This bonus is picked at the time of scribing from the list of special weapon abilities from the DMG. It takes 5 rounds x the level of the spell slot given up to scribe this rune. This enhancement lasts 1 minute per level of the spell slot given up.

Runecast: You can cast a spell of a level up to your Runecaster level into a rune that is triggered when a preset condition is met. The spell cannot be from the Illusion, Divination, Abjuration or Transmutation schools. The condition can be as simple as “go off when someone reads the rune” to as complex as “go off when a paladin reads this rune”. There can be up to three different conditions. Each condition beyond the first adds 5 rounds to the scribing time. Scribing a Runecast spell takes a number of rounds equal to 5 times the level of the spell. It costs 10 XP times the level of the Runecast to scribe the rune in addition to 20 gp in special ink.

Runic Knowledge: At the 2nd and 4th levels a Runecaster can either add a number of spells with a runic component to his spellbook or his list of spells known equal to his Intelligence modifier.

Suppress Rune: To a maximum of twice per day a Runecaster can suppress a spell with a runic component for a number of rounds equal to his Runecaster level with a successful Spellcraft check. To use this ability a Runecaster must be aware of the rune.

Runes: At the first, third and fifth levels the Runecaster gains knowledge of a number of runes with great arcane power. He can scribe these runes a number of times per day equal to his Runecaster level plus his Intelligence modifier. These runes cost 20 gp worth of special ink to scribe and take 5 rounds to write. The saving throw is equal to 10+the Runecaster level + the primary spellcasting ability (Int for Wizards, Cha for Sorcerers). All runes last for a number of rounds equal to the Runecaster level +spellcasting ability modifier. These runes must be scribed on a person’s skin like a tattoo to be effective unless otherwise noted. A subject can have only 2 runes active on them at any given time. If they exceed this number than the two most recent runes stay in effect while the rest fade.
Rune of Protection: This rune grants a +4 bonus to the subject’s
Armor class.
Rune of Health: This Rune grants the subject 10 temporary hit
points.
Rune of Strength: This rune grants the subject a +2 bonus to
strength.
Rune of Dexterity: This rune grants the subject a +2 bonus to
dexterity.
Rune of Fear: This rune forces all opponents within 10 feet to make
a DC 14 Will save or become shaken for the duration
of the rune as long as they can see it.
Rune of Skill: This rune gives the subject a +2 bonus on all skill
checks.
Rune of Speed: This rune grants a +10 bonus to the subject’s speed.
Rune of War: This rune grants a bonus on the subject’s base attack
bonus equal to Runecaster’s level. The subject’s base
attack bonus cannot exceed their Hit Dice.
Rune of the Rogue: This rune allows the subject to sneak attack as
a first level rogue. If cast on a Rogue it
increases the damage done by their sneak
attack by 1d6.
Rune of the Healer: The subject of this rune can use the Lay on
Hands ability as a Paladin of their level.
Rune of Elemental Resistance: This rune grants the subject
resistance to the selected type of
energy. The resistance equals the
Runecaster’s level plus 2.
Rune of Persuasion: This rune grants a +4 bonus on all Diplomacy,
Intimidate and Bluff checks.
Rune of Escape: This rune allows the subject to use an effect
similar to Dimension Door except that the
target area must be within fifty feet and visible to
the subject. This rune is expended once used.

You have come together from various corners of the known world for a variety of reasons. You have decided to explore the long abandoned Grimmbold Manor in search of wealth. Grimmbold Manor is in an out of the way part of the world called Sachura that has remained relativley untouched by the great wars that have torn the rest of the world to pieces. You now stand at the crossroads that will take you into the Sachura region. You must choose either to go left to the small town of Greenhollow to gather supplies and perhaps information on Grimmbold Manor or to go right which will take you directly to Grimmbold Manor.
Good luck, Arctaris