King Arthur Pendragon is an RPG in which players take the role of knights taking part in quests, tournaments and pining after courtiers in, well, King Arthur's England. Written by Greg Stafford and published by Chaosium, it has gone through a number of editions (notable skipping a second edition since Stafford wasn't overly fond of what he was seeing so he scrapped it and went straight to a third edition). It has passed through the hands of a couple different companies, first Green Knight Publishing then White Wolf then to Nocturnal Media. Chaosium, though, got it back in 2018 and got Stafford back just before he died to make the 5.2 edition.
After it was published in 1985, Pendragon won several industry awards, and reviewers highly recommended it; in following years, it was included in numerous "Best of" industry lists.
Pendragon has been lauded by pretty much everyone and has gotten as many awards as one of those Communist Russian generals have medals pinned to their chest (namely, A LOT). It's often considered one of the best RPGs out there but with a major caveat - the system is built to help facilitate a retelling of the Arthurian legends so a lot of things cannot be changed by the characters. Arthur will always become king, Guinevere will always fall in love with Lancelot, Galahad will always find the Holy Grail, and the Saxons will always be assholes.
The characters will have a large number of statistics, the core of which being their personality traits which are a set of thirteen opposing traits for things like Modest/Proud and Temperate/Indulgent. Each pair of traits will have 20 points allocated between them, almost all of them being determined by your character's culture and faith.
Then you have passions, things that drive your character such as "love for king," "love for family" and "seriously, fuck those Saxons. Next one I see I'll bash their fucking face in, I swear on me mum I will!"
You also have skills which range from the typical fighting skills like swordsmanship to more niche things like playing the lyre.
You also can have magic if you have the right supplements and you can alter your culture and faith as well so you could be from Aquitaine (Southern France), Byzantine (Eastern Roman Empire successor state based modern in Greece and Turkey) and Zazamanc (basically North African Berber). There are also rules for playing a Lady of the Court (if you're not keen on playing a knight or you don't have a male heir, more on that in a moment) or even having faerie blood in you (which is not as fun as it sounds since fucking church bells can really screw with your character).
Each game session covers one in-game year (though sometimes you may need to do two sessions to cover that one year if you're on a particularly harrowing quest but need to stop for the night or something). The total number of sessions before the campaign is complete is about 90-100 sessions, so well over one year typically of IRL gaming. At the end of each session is the Winter Phase where your characters wine and dine with other knights and nobles, set up alliances and agreements, tend to your holdings, get married and have kids. Because of the length of time it's expected for the game to go, you're supposed to build a line of heirs to pick up and carry on the family legacy. It's fully possible to play a pagan knight under King Uther who dies, his Catholic son then taking up the family arms to try and carve out their own petty demesne before bending the knee to King Arthur, their daughter then going off to Camelot to rub shoulders with the ladies-in-waiting at court only to fall in love and marry a faerie knight and have their son become a Knight of the Round Table who goes questing with Galahad for the Holy Grail only to later see King Arthur ushered off to Avalon. That's just one path, but all sorts of crazy shit can crop that can make all that change.
The whole system is also based on a simple roll-under mechanic for any of your traits and usually opposed rolls for your skills. It's not hard though the character sheet and rulebook could do more to make things look a little easier.
Character Creation Guide
In order to make things less overwhelming, here's a basic guide to character creation. This assumes 5.2 Edition, and hopefully some updates will be made for 6th when it comes out.
The main cultures are Cymric (Most of Britain), Irish (Ireland), Roman (Cities), Picts (Jagent and the North), Saxons (Surrey, Bennoc, and the Saxon Lands), and Aquitainian (Aquitaine). If you don't know what to play or just want the standard, play a Cymric knight. Irish are Cymric without Spear Expertise, Picts tend have interesting backstories and habits but are screwed over by dogshit Attributes, Romans are good healers and talkers, Aquitainians are every Frenchman stereotype in one, and Saxons are budget Vikings who about half of Logres gets to hate. In short, play Cymric.
Continental Cultures are interesting, but playing one is the equivalent of playing a Drow in D&D. That being said, try playing an Occitanian sometime. You literally get liking wine as your special ability.
There are way too many homelands, so I'm just going to include broad categories.
Logres: The main kingdom, run by King Uther at the game start. It's a cool place, at least until (spoilers for a centuries old story) he dies.
Cornwall: The only place where you can start as Pict at game start. It's pretty cool, and also has some pagans. Brittany is also later included.
Cambria: Modern Wales (and notably a place where you can actually meet people who speak the language the Cymric people are speaking in modern times), it's actually pretty lit up here. Notable for some tribal Cymric.
Cumbria: Wanna get raided by the Picts? Start here.
The North: The North is only available later, but it's actually pretty cool. Lothian is basically the modern Scottish Lowlands, with the Picts living in the Highlands.
Other Places: There's some other places in Mainland Europe, as well as "Zazamanc Land" and "Hunland".
Traits and Passions:
This is pretty freeform. Be sure to bump up what you want, and remember that you get annual Glory bonuses for traits and passions of 16 or higher, which is really good. Getting your religion bonus is nice but not necessarily a must-have if it conflicts with your character concept; remember that high traits and passions are also means for you to lose control of yourself.
The Attributes are Strength, Size, Constitution, Appearance, and Dexterity. Appearance's usefulness strongly depends on whether or not your GM will ever have you roll it. Dexterity is useful for moving fast and not falling down like an idiot. Constitution is useful for not dying. Size is good for derived statistics, but is almost never actually rolled. Lastly, Strength is the most useful in general. If I were you, I'd invest in Size and Strength, but that's just me.
Here's a list of some skills that will come in handy.
Flirting/Romance: This is how you're going to get a wife. Remember that having babies is an important part of the game.
Hunting: Remember that this is the main pastime of knights.
First Aid: This keeps you from dying, so you should learn it.
Battle: This is how you're going to win mass battles. Go for this one.
Horsemanship: The skill of not falling of a horse and dying.
Lance: This is generally better than spear, because lance charges will kill almost anything if you can hit it right.
Racial Skills: Most of these are pretty useful. Of all of them, the Saxon Two-Handed Weapons, the Cymric Spear Expertise, and the Zazamanc Medicine are the most useful. Others are a little more situational, although Roman Law and Dane Seamanship can be godly for some games.