Conan RPG vs D&D
While both Dungeons & Dragons and the Conan RPG are based on D20 mechanics/skills/feats, there are several none-too-subtle differences between the two game system. For those looking for a short primer rather than wanting to read the entire ruleset here are the major differences in a nutshell.
Character Creation
1. All races/cultures have prohibited and favored classes. There is no experience penalty for multiclassing.
2. Prohibited classes cannot be taken at first level, but if given opportunity can be learned later i.e. a landlocked barbarian culture may have Pirate as a Prohibited Class, but could pick up the class later if the character had an opportunity to serve on a ship.
3. Favored classes give you a bonus feat for the first and every 5th level (including combinations of favored classes). So if you have favored classes of scholar and noble, and took Noble at first level, you would get a bonus feat then. If you took three levels in Noble and then two in Scholar then at level 5 you would get another bonus feat, as you have 5 combined levels of favored classes.
4. All races will have several "Background Skills". These are skills you get ranks in before you even apply your your first Class level. These ranks still count towards maximum ranks in class/cross-class skills, so sometimes a racial bonus to skill checks is better than extra ranks if you really want to excel.
5. Skills - Your class' skill points may be used for class skills on 1:1 or cross class skills 2:1. Your skill points for your Intelligence Bonus may be used for any skill 1:1.
6. Magic Attack Bonus - this is like a BAB for magic. It's referenced a lot for Feats and Sorcery Styles
7. Dodge/Parry Bonus - these two values reflect how well you parry (avoid getting hit by deflecting the weapon) or dodge (avoid getting hit by getting out of the way of the weapon) in combat. Armor provides Damage Reduction rather than making you harder to hit, so you'll want to pay attention to these values. Your Parry is modified by your Strength bonus and Dodge is modified by Dexterity bonus.
8. After level 10, you gain a specific number of hit points based on your class rather than a full hit die.
Combat
1. As mentioned above, there is no "Armor Class (AC)" value to target to hit. You choose to defend by Dodge or Parry. Shields add to Parry Defense value. Dodge Defense requires there is room to manuver/roll with the swings, so if there is none there is a penalty to a Dodge defense.
2. Armor (including helmet) provides Damage Reduction, many animals and other creatures will have a base DR from "natural armor" or thick skin. Armor is "a good thing". You can trust to a high dodge/parry to not get hit, but if you do and have no armor - it will hurt.
3. Weapons have an Armor Piercing factor that can, if enough damage is done, partially bypass the DR and concievably even lower the DR until the armor is repaired.
4. Finesse - a special attack can be made to attempt to bypass armor by aiming for unprotected areas or sliding a weapon between plates with certain weapons, notably piercing or pointed slashing weapons. If a finesse attack hits, it ignores the DR from armor.
5. Beware of feints. An attack delivered that catches you unawares, especially a finesse sneak attack from a thief or pirate, can be deadly. Do not ignore the skill Sense Motive at your own peril. There are a few house rules about defensive fighting adding to Sense Motive for watching out for Feints.
Magic
1. The magic (sorcery) system is closer to the D&D Psion "power point system", but most spells are not to be used in combat.
2. Magic is available via two methods, the Dabbler feat, which gives some low level access to various magics and the Scholar class. The Scholar class does not automatically make one a sorcerer. Sorcery styles and Advanced Spells can be spent instead on various other feats and advantages. A Scholar is as likely to be a sage, alchemist, or priest as he is a Sorcerer.
3. The Scholar has several backgrounds (adept, demonic pact, independent, etc) that speak to the source of thier magic.
4. Magic points are regained through rest, meditation, as well as drugs/herbs, sacrifices, etc. Sorcerers have a bad reputation for a reason.
5. While there are "priests", it is more of a religious significance. There is no divine magic that is for channeling healing. i.e. A scholar or priest is not a D&D Cleric. If you get maimed, don't expect someone to lay on hands and have you back to new before you move on. The Healing skill has has several applications and you will recover hit points with rest, but be aware that wounds can be serious.
6. Sorcery - The magic system in the Conan RPG has various "Styles" and "Spells". Think of them as "paths". In taking a new Sorcery Style, say Necromancy, most of the higher level spells, like Death Touch, require either certain Feats or previous spells in the Style be known. Scholars get both "New Sorcery Style" and "Advanced Spell" as class benefits as they level up.