Naturally, this domain only works in the Birthright setting, and most specifically with the conversion I made.
The Bloodline domain is available to any deity of Cerilia. Its exact tenets vary from faith to faith, but those who follow this religious doctrine are sought out for their expertise in matters of lineage and inheritance. Some are scholars of the divine bloodlines, and others are holy (or unholy) champions venturing forth to battle blooded foes.
The domain's mandate means that even clerics of opposing faiths and gods will meet to share knowledge and records of the scions they meet in their travels, or catalogue the affairs of powerful blooded entities, the awnsheghlien and fabled ersheghlien.
Bloodline Domain Spells1st - amanuensis, detect divine blood
3rd - enhance ability, zone of truth
5th - clairvoyance, tongues
7th - death ward, locate creature
9th - blood boil, legend lore
Archivist of Lineages
Your clerical order is extremely proficient in the histories and relationships of noble bloodlines and keeps a quasi-religious text with them at all times known as the Archive of Lineages. Each cleric maintains their own copy of the Archive, which contains abbreviated family trees and major historical events regarding some of Cerilia's most storied families.
It is the duty of each Archivist to catalogue the affairs of scions they encounter, and expand their copy of the Archive. If the cleric's copy of the Archive is damaged or destroyed, their first priority must be to repair the book or create a new copy to take with them on their journeys. Without it, the cleric cannot prepare any new spells.
When you choose this domain at 1st level, you gain proficiency in History. If you are already proficient in History from another source (such as being Anuirean) you instead gain proficiency in Persuasion.
You also gain proficiency in heavy armor.
At 1st level, you possess the knowledge of how to more effectively engage blooded foes. You gain a +2 bonus to damage rolls with weapon attacks against creatures with a bloodline score. Additionally, you have advantage on Wisdom (Survival) checks to track blooded individuals, as well as on Intelligence checks to recall information about them. Furthermore, you have advantage on saving throws against effects from a scion's blood abilities.
Channel Divinity: Blood Augment
When you reach 2nd level, you may use your Channel Divinity to boost the effects of a bloodline's power. As an action, you may choose one target within 60 feet of you that possesses a Bloodline ability score. For 1 minute, that target adds their Bloodline modifier to the result of attack rolls, skill checks, and saving throws. If you are a blooded scion, and your target either lacks a Bloodline score or their Bloodline score is weaker than your own, you may instead apply your own Bloodline modifier in place of the target's modifier.
Starting at 6th level, when either you or an ally within 60 feet uses a blood ability, you and all allies within 60 feet of you gain temporary hit points equal to three times the Bloodline modifier of the individual activating the ability.
At 8th level, you gain the ability to infuse your weapon strikes with divine energy. Once on each of your turns when you hit a creature with a weapon attack, you can cause the attack to deal an extra 1d8 radiant damage to the target. When you reach 14th level, the extra damage increases to 2d8.
Upon reaching 17th level, the cleric gains special powers as they relate to the ebb and flow of bloodlines. By spending at least 1 hour with the corpse of a slain scion that has been dead for no longer than 1 week, the cleric may transfer that scion's Bloodline to a new unblooded recipient. This recipient must be present for the rite, and the departed scion cannot already be divested of their divine blood by another source (such as being slain by a tighmaevril weapon). The recipient immediately gains a Bloodline score of 11 with the same derivation of the slain scion. If the slain scion's Bloodline score was less than 11, the recipient's score is equal to that value. If the dead scion is later returned to life, they will do so without their bloodline!
This does not give the recipient stewardship of the scion's holdings or provinces, though the recipient may later attempt to lay claim to them as the "blood heir" of the departed. The ceremony of investiture must still be performed to formalize the transference.
The cleric may not use this ability more than once per week. Some faiths view this as a masked form of usurpation if used irresponsibly and will react accordingly.
There's a few places I see improvement needed. Bloodline Transference is an "in-the-field" version of basic investiture mechanics, but comes very late in the domain's progression and thus I didn't see this as a huge danger. It's not a combat benefit, which may make this domain lag a bit behind in raw power compared to some others.
Also, Bloodbane's damage bonus doesn't scale well as-written, so I also tinkered with it adding the cleric's Wisdom modifier to damage. It still might not be good enough, so I am considering improving it at level bands (+4 damage at 6th, +6 damage at 11th, +8 damage at 17th).
Archivist of Lineages is a pure ribbon. I loved the idea of the wandering priest with the huge tome bearing the names of every noble family tree from Anuire to Vosgaard and having the sacred duty of chronicling every offspring, legitimate or otherwise. Whole adventures could arise from the need to learn the truth about a given regent's progeny, or urging (after first finding) a bastard scion to take up the mantle of rulership to vanquish a corrupt parent.
These were made to support the above domain. There's also like a thousand versions of amanuensis out there. Mine's probably too stingy for a first level slot, so I'm leaning towards increasing its duration to an hour, adding it to the wizard spell list, and making it a ritual.
Casting Time: 1 action
Range: 30 feet
Components: V, S, M (a quill with a silver point worth at least 10 gp, plus adequate parchment or paper to complete the copy)
Duration: 10 minutes
By means of this spell, you may copy written texts from any non-magical book, parchment, or other written medium. The quill that is the component of this spell animates and rapidly transcribes the text as a perfect copy of the original over the course of the duration, completing one page per minute (up to ten pages per casting of the spell).
The spell cannot copy diagrams or illustrations, nor can it transcribe magical texts, duplicate spell scrolls, or create glyphs of warding. Where such banned items occur, only a blank space will be revealed in the copy.
Casting Time: 1 action
Range: 60 feet
Components: V, S, M (a small vial of snake venom)
Duration: Concentration, up to 1 minute
This spell, created as a bane to blooded scions and awnsheghlien everywhere, ravages the body and cripples the victim's divinely-gifted abilities. Choose a target that you can see within range that is not undead. The target must succeed on a Constitution saving throw or suffer 5d6 points of fire damage and 5d6 points of poison damage as their blood becomes a burning toxin within their veins. If the target is a blooded scion, the damage is increased to 5d8 fire and 5d8 poison.
On the initial round that the damage is suffered, the victim cannot activate any blood abilities or use powers related to their divine heritage. At the end of each of its turns, for as long as you concentrate, the victim can attempt another Constitution saving throw to end the secondary effect.
Detect Divine Blood
1st-level divination (ritual)
Casting Time: 1 action
Components: V, S
Duration: Concentration, up to 10 minutes
For the duration, you sense the presence and location of individuals possessing a bloodline within 30 feet of you. If you sense a bloodline in this way, you may use your action to pinpoint individuals with a bloodline of any strength, determining its derivation and relative strength (tainted, minor, major, great, true).
The spell can penetrate most barriers, but it is blocked by 1 foot of stone, 1 inch of common metal, a thin sheet of lead, or 3 feet or wood or dirt.