the carcosine codex

The book itself is not unusual yet distinctive. Sturdy covers of tawny reptilian leather with buff vellum pages stained with saffron wrinkles,  The archaic, angular sepia script is painstakingly written and illustrations of curved angular lines, reptilian iconography and circles are traced into the margins.  A cursory glimpse of the text reveals there is mystical lore and references to many worlds and their echoes.  To read it is a significant undertaking as the book requires a week's dedicated study to unlock it's secrets, yet once those secrets are unlocked, further consultation is needed to use them.

Scholars and magicians fervently seek it.  The book has merit, it provides the following rituals: consult mystic sages, enchant magic item, hallucinatory creature, hallucinatory item, wizard's sight.  It is possible to learn the rituals from the book but the Carcosine Codex offers darker power yet.  Some think it accursed, best avoided or destroyed, others announce profound revelations, a prize without equal. The Codex has been described as a 'pox of the soul' and it's effects mirror that of a disease. Those who have read it claim horrific visions of a mist-shrouded city by a lake under an alien night sky.

Carcosine Degeneration (Level 14 Disease) Attack: +18 vs. Will. 
Insight: Improve DC 27, Maintain DC 22, Worsen 21 or less.
Note the time to study the Codex requires seven Will attacks in addition to any time spent studying the rituals contained within the book.  Exposure is triggered by reading the book or using it as a ritual book, merely owning it isn't sufficient cause. Also note that Insight, rather than Endurance is used to resist the degeneration. It has been known for certain magicians to actively resist aid from the degeneration, claiming that their condition provides them with powerful insights.

Healthy
No adverse effects.  The book contains the rituals above. 

Initial Effect
Lose 1 healing surge from unsettling dreams of a mist-shrouded city by a lake under an alien sky at night.
Take a -1 penalty to Will defence.
Gain a +1 bonus to Arcana and Perception checks.

Secondary Effect
Gain a +1 bonus for attacks with necrotic and psychic keywords.
Gain a +2 bonus to Arcana and Perception checks.
Take a -2 penalty to Will defence from delusional thoughts.
Lose 2 healing surges from disturbing dreams of being stalked through the mist-shrouded night-time streets of the city by a shrouded figure clad in rich yet tattered clothing.

Final Effect
Gain a +3 bonus to Arcana and Perception checks.
Take a -4 penalty to Will defence from delusional thoughts.

Lose 4 healing surges from a recurring nightmare where the shrouded cadaverous figure in rich, tattered cloth of gold and samnite catches you at the lake's edge.  It rasps the lich transformation ritual in your ear from it's rotting lips.  To effectively study the ritual and add it to the list of mastered rituals requires eight nights at this stage.  If cured, you retain mastery of the ritual.

(inspired by Robert W. Chambers and taichara's Book of the White Cat).