D100 is simple enough already. You roll 2 ten-sided dice. One is tens place (00-90) and the other is ones (0-9) and you try to get a result under your skill level. The lower the result the better. So if you have a skill of 80% you just gotta get under 80. A skill at 30% means you gotta get under 30 and that's harder to do. 1's (00 on tens and 1 one ones) are critical successes and 100's (00 on tens and 0 or ones) are fumbles. In d100 the result of the tens die tends to be the most important result. The ones is just if you're barley on the edge, opposing sides got a tied result, and to determine if you got a critical or fumble. In OpenQuest there are modifiers but you don't have to keep up with a bunch of little ones. All modifiers are either +/-25% or +/-50% with the exception of some spells that are +/-10%. This gets rid of a lot of micromanagement that plagues RPGs and can sometimes be a hassle in percentiles.
Character creation is simple but different than RuneQuest. Gone are lifepaths. I don't know if this was done for simplicity or because of the way skills are laid out. Maybe both. It's a good different alternative from what is common in BRP. Each character has starting characteristics. There's eight characteristics each with a base point value of 8. Strength, constitution, dexterity, size, intelligence, power, and charisma. Players have 30 points to spend on them. All have a maximum value of 18 for humans. Characteristics can be reduced lower than 8 for some additional spending points but have set minimum values. If a player has a concept in mind this is the best method. There's a dice rolling method too if a player wants to go completely random. Attributes are second values that are directly effected by characteristics. Damage modifier, hit points, major wound level, magic points, and movement rate. There are different character creation rules if a player wants to play a non-human. It's very easy to use any non-human as a player character. From the common elves and dwarves to monsters. I played a game where the players were in a orc war-band. 2 were orcs, 1 goblin, and the other 2 were different types of undead. It's a simple and robust system.
Skills are also different than other d100 games. The skills are more broad to again cut-down on micromanagement. This is classless game but the skills are almost like career fields. This makes the characters feel more experienced and like they took an actual trade rather than picking up random skills. I like this approach because it's still more robust than classes but less hassle dealing with specific skills. When a skill is raised it's raised in increments of 5% to cut down on math and for simplify. It would be very easy to add your own skills if something you want can't be used with the skills given. I think this modification to skills is what lead to most of the major mechanical differences from RQ/BRP.
Magic is different if you're not familiar with RQ. Magic is open to everybody. Now that's easy to change if you don't want that but it was this way in RQ and it's that way in OQ. It's not bad though. It's common magic and it's fairly simple stuff. A character with just common magic isn't going to be a spell slinging wizard. It makes sense though. In the real world anybody can be a fighter but unless you specialize in fighting you're not gonna be better than average. In OQ there's Sorcery and Divine magic. These are the specialized magic fields and where more powerful spells are but they have more requirements to meet. Shamanism and the spirit combat rules to go with Shamanism are also included. So there's a lot of variety in this game when it comes to fantasy magic all using the simple and robust OQ philosophy. Keeping up in RQ tradition is the influence of religions and cults. Different gods and practices give different skills, spells, and special abilities but also require their followers to do things to appease them. Cults are more influential on Divine magic but they effect the social views of all characters and the setting one way or another.
Combat is fast and gritty. Players have a list of different combat actions. Defense, close, ranged, and unarmed all have a set of actions. When fighting the opposing sides roll. The one with the lowest roll wins and is successful with their action. If taking a defensive action the offensive attack is avoided. If taking offense they roll damage dice according to their weapon and the if the opposition is wearing armor a fixed value is subtracted from the damage. OQ uses a fixed hit points system as opposed to hit locations like most BRP games. If a character receives damage that is more than 1/2 of their original hit points in one hit the victim has to roll for a critical wound which will be nasty. Mangled limbs, loss of a limb, brain damage, eye torn out, and broken bones. These are like the Stormbringer 5th edition rules and fit right in with the simple minimal counting approach of OQ. I really liked this change and it made combat brutal without being a chore like how hit locations can be. Fantasy settings tend have a lot of fighting but in OQ it shouldn't be the only option characters have to solve a problem.
Improving a character in OQ may seem a bit slow than other RPGs but keep in mind characters start out being proficient to begin with. This might just be my opinion because BRP games never really focused on maxing characters out so much they essentially just become stat blocks with no personality or drive. There's similar rules in OQ like the previous mentioned Burning Wheel called motives. These are different than beliefs but their purpose is the same overall. To give the characters goals to accomplish and to be rewarded for them. It's a different improvement method than most BRP games but just as effective. It's more story-driven in OQ and I think that was the author's intent. Players can practice skills outside of questing to speed improvement up. There's also hero points which allow the player to change the situation they're in through plot editing.
There's more rules for ships, mental damage, travelling, mounts, objects, healing, poisons, disease, encumbrance, suffocation, thirst and starvation, falling, illumination, and burning to death. These are all towards the back and are only needed when the situation comes up. They're all simple to apply and can make a situation more interesting in gameplay. In the back is also the monster list and the information needed to use them as characters. There's also ways to figure up random items or treasure they will have if defeated. There's about 40 in total (counting the elemental separately) and an animal list with another 25. So the selection is really good and making your own creatures here won't be a problem. (I'm glad to see the Durulz from Glorantha here ;)
There's a pre-made setting called the Empire of Gantan. It's a cool base for a setting that GMs can build on. It's like a fantasy Byzantine empire. Religion, conquest, politics, combined with magic and monsters. It's clearly inspired by Gloarantha and I think it's purpose was to make OpenQuest easier to tie in with that setting or to be built on by GMs. It comes with some sample adventures to show off the system and to give a feel of the setting. Not bad for starting out if you're just trying this game out from scratch or need some quick ideas.
You can get OQ at http://d101games.co.uk/books/openquest/. The publisher uses Lulu print on demand so if you order it will take about a week longer than most orders because of the time needed for Lulu to get around printing and binding. OpenQuest is a simple and robust game out-of-the-box but easy enough to customize and add in your own stuff. It's very easy to add RuneQuest and BRP rules if something from them fits your campaign better. This goes along great in the family of D100 games because of it's different twists on the system.
