TurinTurambar
Adventurer
So, at it's most basic Heroquest is an opposed roll system using 1d20 where you try to roll less than your ability but more than your opponent's roll. If you roll your ability exactly that's a critical success; if you roll more than ability that's a failure; if you roll a natural 20 that's a fumble unless your ability is 20. If your ability advances past 20 then it goes back to 1 but you get a level of mastery (W after the number) which shifts your level of success by one or if you have a critical shifts your opponents level of success down by one. An ability of 25 is written 5W, and if you rolled 15 then that's a failure, moved up to a success because of your mastery, and beats someone with ability 17 who rolled a 13 (you both had a success, but your roll was higher).
Characters are very freeform. The main way of creating them is by writing down the three basic keywords that say where your character is from, what their previous occupation was, and what sort of magic they have. Then write a 100 word description of your character, pick out the important bits, and add those to your character sheet as Abilities which start at 13 (you can write more but the rest is backstory and won't be on your character sheet unless your GM is generous). Keywords in most respects are just another Ability and can be used for tests, but they're fixed at 17 in HQG and are quite broad - Homeland: Sartar 17 means that you'd be able to use it to do a check about geography, language, customs, which clans are rivals with others, history and other things that relate to Sartar. You can also use the Keyword to start a specialised Ability, so if your previous career was Craftsman you could have Potter as an ability and write it in under the Keyword, where it would have a starting value of 17 instead of the normal 13 for Abilities. An ability can be anything, so you might have Strong, Hate Greydog Clan, Fear Dark Trolls, or many other things. Abilities can sometimes be used to augment other abilities, adding a fraction of the score where it's appropriate; if your character is Strong 17, they would be able to add 2 (1/10, rounded up) to a fighting Ability if they're in melee combat; or if they're fighting against Dark Trolls, Fear Dark Trolls 17 gives a -2 penalty. You can also get an Ability as a consequence of a challenge even if you win the challenge, and impose something on the loser too. Normally abilities are raised a point at a time by spending Hero Points earned through adventuring and completing objectives (personal ones, group ones, or clan ones). You also define groups in a similar way, so a group would be defined by where it's from, what it does, and what magic it uses, along with extra abilities that make it different from other groups.
Heroquesting is handled by using Abilities as stakes in a contest, and every part of a Heroquest ends with a contest. On the Quest for the Meteor Bow we're doing, the various parts include Finding a Steed; and in that, we're probably going to have to wager our horse Ability against the resistance of a spirit animal that doesn't want to be ridden, and if we win our horse is temporarily augmented by the spirit while if we lose it probably runs off and can't be used for the rest of the quest which could be a real problem if there's a race involved and you have to oturun something on foot instead of mounted. Any Abilities gained (even flaws) are lost at the end of the Heroquest, except for the one that's your final objective. Whatever ability you use there is gone if you lose and would have to be started again. If you succeed, then you can decide what to do with the Ability, so we might pass it on to the clan where it becomes part of the clan magic and anyone can learn it as a magical Ability, or if more than one person takes the challenge and succeeds then some might decide to keep it themselves. One of our players had Eldest Child of the Clan Chief as an Ability and intends wagering that as her stake since she intends giving the magic to the clan; if she loses, people won't remember her status and she will have a flaw related to it but if she wins it will increase permanently by the Augment value of the Bow; my character, if the challenge has already succeeded, will challenge to learn that magic personally, and if I succeed then I'll immediately have access to Meteor Bow magic under my magic keyword at whatever value the ability I'm opposing have. Heroquesting is high-risk but also high-reward
That's the basics, at any rate. There's more to the rules, and different versions of Heroquest take a slightly different approach (Robin Laws' Heroquest allows raising keywords for 2HP, for instance), but it's honestly a pretty simple game at its core. Most of the book is examples of homelands, careers and types of magic, as well as GM advice and examples of enemies, challenges and adventure possibilities.
And how much Glorantha lore do you need to have to run the game relatively well?
Ducks? Mount up, sisters, and ready your bows. An enemy is upon us!
I like this approach!