Archivist

Introduction
Archivists travel the world for obscure lore. Some are dedicated to individual patrons, but most just vaguely nod to the pantheon as a whole. A few seek to plunder the secrets of the gods, maybe even to use against them.

The Archivist should feel somewhere between the Bard, Cleric, and Wizard to use. Depending on the spells she acquires, there may be some Druid flavour too. Her Dark Knowledge abilities help her allies with information, coordinating their assault, but not with the flexibility of a bard. The Archivist is tougher than a Wizard but cannot frontline like most Clerics. She lacks some of the Wizard's cast-all-day factor but has access to more spells and an even wider array of rituals. She can fill the role of both Cleric and Wizard in a small party, or complement a party with both by focusing on her knowledge abilities.

Summary
The Archivist is based on the Wizard class. The differences are outlined in the table below.

Spell Casting
Replace the Wizard spell list with the Cleric spell list at level 1. Your cantrips known, spells prepared and spell slots do not change in number, although you may well have different spells in them.

You may add non-Cleric spells from divine spell lists (Druid, Paladin, Ranger, Cleric Domains) to your spellbook (called a prayerbook). To copy them into your book, in addition to the normal time and gold costs, you may have to barter with an NPC or seek out some rare scroll, especially for higher level spells.

You may prepare and cast these using your own spell slots as of they were your normal cleric spells.

Count spells from short spell lists (those which do not include ninth level spells) as double their level. This means you cannot perform this function with 5th level Paladin or Ranger spells, because they would count as 10th level spells, for which you do not have slots. You could still cast 5th level spells from short lists if they have the ritual tag in their ritual form, though. (You cannot add them to your book unless they have the ritual tag).

Proficiencies
The Archivist is proficient in light armour and all simple weapons.

In addition to your Wizard skills, you may also pick two additional skill proficiencies from the following list and gain Expertise in their use: Arcana, History, Nature, Religion.

Dark Knowledge
You lose the Arcane Recovery class feature. Instead you have Dark Knowledge.

Once per short rest, as an action, you may call out the weaknesses of a creature or creature type you are facing (e.g. 'Pit Fiend' or 'Goblins'). You must first identify the creature(s) with a successful knowledge check. (But see below*)

Each creature takes a Wisdom save (DC=your spell DC). If there are multiple creatures present, each one takes a Wisdom save to adjust their tactics and cover their weaknesses, either when you take your action or as they are rolled against (whatever is convenient at your table). (The DM may roll one save for a group of identical enemies, but should be aware this makes your signature ability less reliable.)

If the creature fails its save, each of your allies who can hear you may gain advantage on one attack roll or ability check against that creature. This advantage must be used within a round. You may take a bonus action on subsequent turns to continue calling out information and maintain this effect. Each ally may use advantage once per round.

To maintain Dark Knowledge advantages requires your concentration (which can be broken like concentrating on a spell, e.g. if you take damage) and for your allies to be able to still hear you. (The DM could rule that against some deaf/unaware/stupid creatures, continuing to speak is not necessary as the enemy are not reacting to the Archivist calling out their weaknesses.)

At 18th level, your allies may use advantage on all attacks and ability checks in the first round when you take your action (not in subsequent rounds). If you sustain the effect, they may still only gain advantage once per round in each round after the first, though.


 * The DC to find an appropriate weakness or information on a creature should start at 15 for humanoids and goblinoids, up to 25 for rare creatures such as fiends (even if the Archivist claims to spend a lifetime studying its weaknesses), or even DC30 for legendary horrors as yet unknown to the world and only even whispered of in the dreams of dying madmen, etc.

Dark Knowldge may reflect instructions as simple as "aim for the eye!" or as complex as "Attack plan delta! Type three cut-off! 40 degrees!" with an experienced team. Obviously some abstraction is necessary to link role play and story elements with mechanical advantages, but I think this is a reasonably well made attempt.

Archetype
At 2nd level, choose an Archetype: Delver or Scholar. See below for details of the benefits per level.

At 2nd level, a Delver receives proficiency in medium armour and shields. A Scholar receives two Portent Rolls (see the Divination Wizard)

At 6th level, a Delver recieves the extra attack feature. A Scholar receives the ability to add rituals from the spell list of any class, arcane or divine, and use them. They may still only be cast as rituals.

At 10th level, a Delver's allies may use her Dark Knowledge to re-roll weapon damage die instead of gaining advantage on an attack or ability check. A Scholar's allies may use her Dark Knowledge on saves against the abilities of the identified creature instead.

At 14th level, a Delver receives Spell Resistance (as the Abjuration Wizard). A Scholar receives an additional Portent Roll per long rest (as the Divination Wizard)

At 20th level, a Delvers mastery of the secrets of death is complete. She has resistance to necrotic damage, advantage on saves against necromancy spells, and may add her proficiency bonus to death saves three times per long rest.

At 20th level, a Scholar instead receives the Darkest Knowldge ability. Her mastery of the enemy's deepest secrets and fears stuns her target, who is lost for words and unable to react to this revelation. Once in a creature's lifetime, when it fails it's save against dark Knowldge, it is stunned for one round and can take no action but to gawp at the Archivist in shock.

Multiple creatures can fail their save and be affected by the stun at a time, although if combat continues with even one other creature, they will recover after their one round of stunning even if others don't (see below).

If after the Archivists use of Knowldge the creature remains unattacked and unprovoked (by allies, rallying enemies, or any combat at all), the Archivist can keep talking, continuing the stun effect while continuing negotiations/interrogations/intimidation of the creator. The creature, upon recovering, will likely blame a traitor or bluff away the revelation.

The DM may allow this to work more than once in a creature lifetime if the target has any particularly juicy secrets and the Archivist can discover more (outside of rolling dice for knowledge)