The Basics
First of all,
This is the SRD, which has all the rules set up so that you can access the sections freely.
Language- I will try to post any DnD terms here
XdY - Such and such a number of some type of dice. 1d6 means 1 six sider, 3d4 means 3 four sided dice, 3426234d20 means 3426234 twenty sided dice, etc.
BAB - Base attack bonus
Str - Strength
Dex - Dexterity
Con - Constitution
Int - Intelligence
Wis - Wisdom
Cha - Charisma
PB - Point Buy
DC - Difficulty Class
AC - Armor Class
Modifier - Any number that modifies your roll
x bonus - A type of bonus. Generally bonuses only stack with differently named bonuses. Examples are Circumstance Bonuses, Enhancement Bonuses, and Luck Bonuses.
/ - A slash (/) often represents the word per. So 1/day means once per day.
HD - Hit Dice, the type and number of dice used for determining hit points of a character. Affects many other aspects of the character as well.
Racial HD - Racial Hit Dice, only certain races and monsters have thes.
Class Level - Your level in a given class
Character Level - Your total level in all classes
LA - Level Adjustment, certain powerful races and monsters get this
ECL - Effective character level, your character level plus your LA
Caster level - Your level for the purposes of determining the effects of spells you cast.
The D20 mechanic DnD is based around the D20 (20 sided die) mechanic. The basic idea is that every task you attempt has a certain likely hood of success, and can be represented by a simple roll: d20 + relevant modifiers. This roll should attempt to equal or exceed the target number or Difficulty Class of the task you are attempting. The most common roles you will encounter are:
Skill checks: 1d20 + ranks in skill + Ability modifer + Armor Check Penalty + Misc
Saving Throws: 1d20 + Base Save + Ability modifer + misc
Attack Rolls: 1d20 + BaB + Ability modifier +Size modifier + misc
Attack Rolls target a special DC called Armor Class. It should also be noted that anywhere in the rules where it says "x bonus" or "x penalty" "to attack" it means this roll, NOT damage unless it is explicitly stated.
A natural 20 (A roll of 20 without modifiers) is an automatic success on Saving Throws and Attack Rolls, but not on Skill Checks.
EXAMPLES:
Mug the Rogue is trying to pick the lock on a door. The DC of the lock is 20 (but neither Mug nor his player knows that). Mug rolls and gets a 10. He has 4 ranks in Open Lock and 20 Dexterity. Therefore, the formula looks like this: 10 (d20 roll) + 4 (Skill ranks) + 5 (Dexterity Modifier, because Dexterity is the
Key Attribute of Open Lock) = 19, causing him to fail his lock opening. Mug decides to try again, but using a better lock pick this time, granting him a +2
Circumstance Bonus. He rolls again, and gets a 9. The formula now looks like this: 9 + 4 + 5 + 2 = 20. Success!
Later, Mug is being attacked by an Evil Wizard. The Wizard casts a Fireball on Mug. Mug has to make a Reflex Save (Reflex Saving Throw) in order to avoid it. The
Save DC of the Fireball is 15. Mug rolls, and gets an 11. His Base Save is 2 and his Dexterity is 20. Therefore the formula goes: 11 + 2 + 5 = 18. Success!
Mug's friend, Chop the Dwarf, is fighting wolves in the woods. He takes a mighty swing at a wolf with his axe. The Wolf's Armor Class is 14. Chop rolls a 10. He has 18 Strength and +1 BaB, as well as the Weapon Focus feat for his axe. Therefore the formula looks like this: 10 + 4 (Strength) + 1 (BaB) + 1 (Weapon Focus) = 16. Hit! Then Chop rolls for damage.
Once you succeed at a task, various thing can occur, one of the main ones being DAMAGE. Damage does not follow the earlier formulas and can vary from source to source.
The Abilities (sometimes known as Attributes) There are 6 ability scores, but they all follow certain rules.
A 10 in an attribute gives no bonus or penalty to actions.
Every
2 above 10 that the score goes, the bonus or penalty it gives to related actions (Called the Ability
Modifier) goes up by 1. This same logic applies below 10. Note that this does NOT mean that every 2 below 10 reduces by one. Both 8 and 9 give a -1 modifier. Here is a small chart showing modifiers for stats up to 20.
0 - 1 = -5
2 - 3 = -4
4 - 5 = -3
6 - 7 = -2
8 - 9 = -1
10-11 = 0
12-13 = +1
14-15 = +2
16-17 = +3
18-19 = +4
20-21 = +5
Average Human attributes are from 8-12.
Strength:
Strength indicates the physical power in a creature. Strength allows you to carry more, hit more often with melee weapons, deal more damage with some weapons, etc.
Dexterity:
Dexterity represents a characters agility and reflexes. Dexterity affect many skill, armor class, hit chance with ranged weapons, reflex saves and more.
Constitution:
Constitution represents physical toughness and hardiness. Constitution grants more hit points, higher Fortitude Saves, and several other things.
Intelligence:
Intelligence represents a characters raw brain power, and ability to understand and manipulate. Intelligence grants characters additional skill points, additional languages known, bonuses to many skills, as well as being the root of some spellcasters' (like Wizards) spellcasting, as well as other things
Wisdom:
Wisdom represents a characters will power, perception and common sense. Wisdom increases Will Saves, is the core casting ability of many divine spellcasters (like Druids or Clerics), and has several other affects.
Charisma:
Charisma represents a characters force of personality and likeability. A charasmatic character could be very attractive, willfull, or just plain likeable. Charisma affects a fair amount of skill as well as being the primary spellcasting attribute of certain spellcasting classes (like the Bard or Sorceror), among other things.
Ability Score Generation There are several ways to generate ability scores, however I will only mention a couple. The first is by rolling. Each player rolls 4d6, and drops the lowest roll, adding the other three together. This is done 6 times, then the numbers are assigned to the Abilities as the player decides.
The other method, and, in my opinion, a fairer one, would be Point Buy. In point buy, all the scores start at 8. Each person gets a certain number of "points" to spend on them (default is 32). Each point in an attribute costs one of your points, until you get to 14. Every ability point after 14 costs 2 points. After 16, each ability point costs 3. The ability scores cannot be raised above 18 at character creation (before racial modifiers). Here is a chart on the cost of a certain score in an ability
8 - 0
9 - 1
10 - 2
11 - 3
12 - 4
13 - 5
14 - 6
15 - 8
16 - 10
17 - 13
18 - 26
Attacks Attack roll have already been explained, but I'm going to go a bit more in depth here. You already should know the formula for attacks. Now, I'm going to explain more about them.
First off, Base Attack Bonus. Characters will have different BaB based on class and level. BaB is added to every attack a character makes.
Secondly is the attribute modifiers. This is what normally would happen, but certain feats and class features can change them.
A melee attack roll adds the character's Strength modifier to the roll.
A ranged attack roll adds the characters Dexterity Modifier to the roll.
If an attack hits, it deals damage. For weapon attacks, it depends on the weapon, and for spells it states it in the spell description.
A characters Strength Modifier is added to his melee damage rolls. However if he wields a weapon in two hands, he gets 1.5 times his Strength Modifier to damage, whereas if he has a weapon in his off hand, it only gets half his Strength modifier to damage.
Ranged attacks do NOT get a character's Dexterity modifier to damage.
A roll of 20 is an automatic hit, and a 1 is an automatic miss. A 20 is also a critical
threat. If a character rolls a 20, they roll again. If that roll would also hit, it is a critical hit, dealing double damage. Some weapons have an
expanded critical threat range. For example, a Longsword scores a critical threat on a 19 or a 20. However, a 19 is not an automatic hit, even if it would cause a critical. Some weapons deal more damage on a critical hit. For example, if you get a critical hit with a battle axe, it deals 3 times the damage.
Example: Chop has decided to attack another wolf. He rolls a 15 + 4 + 1 + 1 = 21, beating the wolf's AC. So he hits. He is wielding a Dwarven Waraxe in one hand, so he rolls 1d10 + 4. He rolls a 6 + 4, so he deals 10 damage. Later, he decides to attack again, this time wielding his axe in two hands. He hits, and deals 1d10 + 6 damage. He rolls a 5 and deals 11 damage. Finally after a bloody battle he is left facing only the lead wolf. He rolls to attack, and gets a 20! He rolls again and gets a 15 + 4 + 1 + 1, getting a 21 and beating the wolf's AC. He criticals! He rolls 1d10 + 6 and gets a 6, so he would normally deal 12 damage. However, he has a critical hit, so he multiplies the damage by 3, getting 36. He swings his axe, and quickly lops off the wolf's head!
Calculating AC Your armor class is a very important part of your character. It governs how hard they are to hit. To calculate armor class start with 10. Add the characters Dexterity Bonus, then their bonus from armor, their size bonus, their natural armor bonus, and any other bonuses they might have.
They also have a Touch AC, which determines how hard it is to touch them. The Touch AC is calculated like normal AC, but an Armor Bonus is not added, as well as some other bonuses.
They also have a Flat Footed AC, which determines how hard it is to hit them while they're flat footed. When they're flat footed they lose their Dex bonus to AC as well as Dodge bonuses and some other bonuses.
