Theonomicon, Shard of Knowledge

I see it all! My mind has expanded to contain the universe! It hurts...I have to relieve the pressure.

— Words scrawled in blood, next to a corpse found with the Theonomicon

Appearance

The book is a beautifully illuminated tome, bound in leather and gold, has holy symbols intricately made with precious metals and gemstones. The symbols subtly shift each time you look at them, a never ending parade of gods.

Identifying

This tome appears to be a "Book of Lore" pertaining to religion. It contains the text of a random religious treatise such as one might find in a well-stocked library. The text changes unpredictably, sometimes remaining the same for weeks, sometimes switching each hour.

An Identify spell or an Arcana check (DC 25) reveals that this is the Theonomicon. It reveals the Proficiency, common knowledge, & advantage features. It also informs them that one can learn powerful secrets from its pages with focused study, but will not grant the details of how that is done or the dangers. The Theonomicon may be attuned with this level of knowledge.

Legend Lore or similar magic will reveal all of the Theonomicon's properties, including the mechanics of Secret Knowledge & its dangers.

Mechanics

Click to expand mechanics

Wondrous Item, Artifact, Requires Attunement

While attuned, the holder has the following benefits:

• Proficiency in Religion. If the creature already had proficiency, their proficiency bonus is doubled for that skill.
• Automatically succeeds on a religion check for "common knowledge" of a deity, demigod, or powerful outsider (typically DC 10 or less)
• Advantage on any religion check related to knowledge of a deity, demigod, or powerful outsider (i.e. demon lords, Archdukes of the Nine Hells, etc.)
• May cast the spell Commune once. Each morning, roll a d6. On a 6, this ability is available again.
• Can use the "Secret Knowledge" feature, see below
• Planar Attunement: The Theonomicon is attuned to the Material Plane and can function as a tuning fork for that plane for the Plane Shift spell.
• Shard of Eternity: This item is one of the Shards of Eternity. When combined with the other Shards, they collectively create the Eternity Sphere.

Secret Knowledge

An attuned being can choose to study further and glean secret knowledge from the Theonomicon, but doing so risks madness.

The reader must study for a number of days, depending on how secret or dangerous the knowledge is (DM discretion)

• Hidden (8 days): Secret teachings of the god told only to the High Priests
• Secret (10 days): Plots known only to powerful outsiders, location of powerful treasures, etc.
• Dire (15 days): The being's greatest fear/weakness, the artifact that can banish them from Toril, True Name of a trusted lieutenant, etc.

Each day the reader must spend at least 8 hours in study of the Theonomicon, at the end of which they must make a Wisdom saving throw DC 16. On a failure the reader takes 2 Wisdom damage and becomes compelled to continue studying for another day (unless they have gained the knowledge they sought). On a success, the reader takes no damage and may choose to stop studying the book. This roll cannot be substituted by features such as portent, lucky, etc., but Inspiration granted by the DM may be used.

Those compelled to study will do so to their own detriment, much like an addict, but not suicidally so. For example, they will lie and manipulate, forego meals, or seclude themselves to avoid stopping. But they may defend themselves from attack, are not forced to kill friends who try to stop them (though they will resist), etc.

The attribute damage can be restored by Greater Restoration, Wish, or similar magic, or by resting (1 point per long rest), but doing so ends the studies prematurely (and will be avoided as such by a compelled creature).

If the creature's Wisdom score is reduced to 0 they are driven permanently mad, their minds completely unhinged by the dread secrets they sought. The symptoms of the madness depend on what secrets were being delved (DM discretion), but nearly always include extreme paranoia and an overwhelming desire to study the Theonomicon, though they can gain no further knowledge from it. Only Wish or divine intervention can restore sanity to such a creature.

If for any reason a day of study is missed, the process must be started again from the beginning.

Destroying the Theonomicon

Rivers of white fluid flow through the Planes of Madness. The book must be submerged in the source spring of one of these rivers for a year and a day to be destroyed, though even this may not be enough to destroy it permanently.

History

Though a powerful artifact in its own right, the Theonomicon is actually the incarnation of one of the Shards of Eternity, endowed with the secrets of the gods. This knowledge is a Dire secret, as is the knowledge of the other Shards of Eternity and the Eternity Sphere.

The Theonomicon was located for a time on the Plane of Knowledge, but went missing at an unknown date and time. It was pursued by the ruling powers of Selgaunt, with the ruler of the city intending to use it to bring Shar back into power. The book was stolen by a party consisting of Mittens, Gerald, Shump Thunderstruck, Marigold, Ice, and Thygrus. Unbeknownst to them, their patron was none other than Grishnak, Champion of Elemental Evil. Gerald managed to leave before the villain revealed his true identity. The rest of the party was attacked, while Ice promptly switched sides and joined the Cult of Elemental Evil. The party narrowly escaped using a teleportation spell cast by Marigold.

Attributes

Type

Wondrous Item

Requires Attunement

Yes

Rarity

Artifact