I will probably be running a game in that genre, but when I do a search, all I get is recommendations for novels.
The genre itself has the following tropes:
1) Knights do all the interesting stuff
2) The crown is fair and good, but bad is done in their name
3) Magicians exist, but are not showy, nor are they quick. Their work can be widespread, but it's going to take them time.
4) Religion is a factor of life, and a grounds for war, but the praxis of the religions is "off screen" - The Christians go to mass on Sundays, but we never watch them do so in the spotlight. The Saxons sacrifice to their gods and seek the wiseman's guidance... again, outside the spotlight.
5) Racism of the human type is prevalent, but not universal.
6) Magic Swords exist, but usually have some drawback
7) No viewpoint non-humans. The Faerie are widely varied, and totally inhuman. But they also are casually cruel, even careless, about the playtoys they make of humans. Forces of nature.
8) War is bloody and ever present
9) if Camelot falls to decadence or the Saxons or some other group, Britain returns to the dark ages. Merlin is the cause of it.
10) Merlin is suspected of not being human in several versions; Morgana, Morgan, and Morgawse may or may not be separate people, but it's rumored that they're part demon or part elf.
11) The Chosen of the Fates: there is one being chosen to be the protector of enlightenment. Canonically, this is either Arthur (most takes) or Merlin (in a few modern takes). Or, in
I Mordred, Mordred.
12) The Big Quests are both important in setting and also strongly allegorical.
13) the downfall begins in Hubris. Arthur's disinterring the head of Bran, Lancelot's affair with Guenevere, The families of Knights feuding with each other.
14) Pageantry beside poverty...
OK, so the system will probably be Daggerheart. The actual setting will be Ravenloft. Yes, I realize neither of these scream Arthurian. Yes, I realize that my lack of knowledge of the genre isn't helpful. Anyway. I'm planning on running in Nidala/Shadowlands (which is described as Arthurian) and connect some other domains with similar feelings to create a cluster.
So keeping that in mind, what would you recommend. Keep in mind, I can make anything into horror, so you don't need to limit yourself to Arthurian horror ideas. Anything will do.
Arthurian really doesn't present a lot of horror elements.
The best movies for reference:
Excalibur,
First Knight,
Tristan & Isolde (acting's so so, but the visuals are very period). Disney's Sword and the Stone is decent if more fantasy.
The Name of the Rose is excellent, if not properly Arthurian, just like T&I.
Arthurian Games: Everyone's already mentioned Pendragon. it's got a great timeline to steal.
Scott Malthouse's
Romance of the Perilous Land has a similar, but earlier set, timeline, and a ruleset that looks hybrid of Dragon Warriors and D20.
I, Mordred. Hard to find, but an excellent adaptation of Arthuran to D20; add
Noble Knights and
Noble Steeds, and you get a decent Arthurian D20 (D&D 3.x) experience.
Chivalry and Sorcery, Wilf Blackhaus. (several publishers). It's grounded in arthurian, but is more properly medieval.
The books of note, of the so-called canon:
Mallory, Sir Thomas,
Le Morte d'Artur - get it in a translated edition for easier reading.
de Troyes, Chrétien,
The Arthurian Tales – a series of ballads and tales collated.
Geoffrey of Monmouth,
Historia Regum Britanniae —
History of the Kings of Britain The real point where Arthurian takes hold.
Nennius,
Historia Brittonum – The birth of Arthur as a legend.
unknown.,
Mabinogion – Old Welsh tales, worked into later canon
Waite, Arthur Edward,
The Vulgate Cycle of the Holy Grail, tr of
Prose Lancelot (unknown authorship)
Some that Arthurian fans argue about:
Bradley, Marion Zimmer,
The Mists of Avalon (and sequels) - Very feminist, Pendragon does include elements, carefully, from it.
White, T.H.,
The Once and Future King – Filled with anachronisms. Still, Pendragon incorporates elements of it.
Lawhead, Stephen R,
The Pendragon Cycle (Taliesin,
Merlin,
Arthur,
Pendragon,
Grail,
Avalon)
Tristan & Yseult. This is not properly arthurian, but tropewise fits, and it's fun. Last I heard, Greg Stafford had not incorporated any of it.
Shakespeare, William,
The Most Excellent and Tragical Historie of Arthur, King of Britain discovered in 2010. I personally haven't read it, but I've seen arguments for and against.
One that I love for a quick trip into a more realistic Arthurian tale:
McCaffrey, Anne,
Black Horses for the King. This is a short small form factor book, but it's excellent and gritty...