DnD 5e Ruleslaw

The Six Ability Scores (And Associated Skills)- These ability scores- strength, dexterity, constitution, intelligence, wisdom, and charisma- are measured on a scale of 1 to 30, with a modifier from -5 to +10 being assigned based on the specific score. Each ability score represents one aspect of your character, and how good they are at tasks relating to that aspect.

Ability Score -> Modifier
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
22-23 -> +6
24-25 -> +7
26-27 -> +8
28-29 -> +9
30 -> +10

Skills are more specific areas of knowledge and expertise, each one tied to an ability score, sharing that ability modifier unless otherwise added to or subtracted from. The list of skills is the same as vanilla 5th Edition DND. (Constitution has no skills associated with it.)

Ability Score -> Related Skills
Strength -> Athletics
Dexterity -> Acrobatics, Sleight of Hand, Stealth
Intelligence -> Arcana, History, Investigation, Nature, Religion
Wisdom -> Animal Handling, Insight, Medicine, Perception, Survival
Charisma -> Deception, Intimidation, Performance, Persuasion

	Using these ability scores or skills mean either making a check or doing a saving throw, both requiring a roll of a d20, and adding the appropriate modifier to the roll. These have a set Difficulty Class (DC), that the result must either meet or be higher than to succeed at that check or saving throw.
	The modifier used for a saving throw of a certain ability score may be different than a check using that same ability. Skills are generally not used for saving throws.
	Sometime, a passive ability or skill score will be called for. The most common case of this is the passive Wisdom (Perception) check. To create this score, add 10 the appropriate skill or ability modifier.

	Proficiency and Tools- You have a proficiency bonus that scales with character level. You may be proficient in certain skills, with certain tools, weapons, armor, and vehicles, or in an ability saving throw. When your proficiency applies to a roll, you add your proficiency modifier in addition to the roll itself and other ability or skill modifiers.
	Some ability scores call for a character to have a certain set of tools on them. For example, picking a lock requires lockpicks/thieves’ tools. Many tools will be returning from Core 5th Edition, but others will be new, made for the setting.

	Movement- Movement is based on a square grid, where each square is five feet by five feet. Each character and monster has a speed score measured in feet, and can move up to that distance per round, and is mainly used for combat and other similar scenarios.
	Certain effects can lower the distance you can move in a turn. Difficult terrain costs 2 ft of movement for every 1 ft of difficult terrain your character moves through, effectively cutting your speed in half while you are in it.
	There are two other types of movement from basic walking and running- climbing and swimming. Some creatures and PCs have a climbing and/or swimming speed, which they use when using that type of movement instead of their normal speed.
Creatures without a climbing or swimming speed spend 2 ft of movement for every 1 ft of climbing or swimming, halving their movement. Difficult terrain costs 2 ft of movement extra when climbing or swimming, which further halves your movement if you do not have climbing or swimming speed.
At the GM’s discretion, you may be required to do an ability check to use either of these movement types in certain environments- such as a Strength (Athletics) check to climb a slippery slope.
	There are two more types of movement not regularly available to PCs and most monsters- burrowing and flying. If you do not have a burrowing speed, you cannot burrow at all. The same principle applies to flying.

	Advantage, Disadvantage, and Criticals- Certain events can cause you to have advantage or disadvantage on a roll. When you have advantage on a roll, you roll two d20s and take the higher. With disadvantage, you do the same, but take the lower one instead. You either have advantage or you don’t- it does not stack. Neither does disadvantage.
	Rolling a 1 is a critical failure, meaning you automatically fail the roll regardless of modifiers. It can have other side effects, which is the Game Master’s choice. Conversely, rolling a 20 is a critical success, which means you automatically succeed.

	Combat and Initiative- When combat breaks out or other similarly threatening events occur, (such as the activation of a complex trap), the first thing the Game Master is determine if anyone is surprised. This can be done in many ways, including checking everyone’s passive Wisdom (Perception) score, or a saving throw.
	Then, everyone determines where they are positioned. This can be done in varying levels of detail- you may use a map, but it is not mandatory.
Then, all individuals involved roll initiative. This involves rolling a d20 and adding one’s initiative modifier to the roll. Your initiative modifier is your dexterity ability score modifier, sometimes added to or taken from by a certain trait of your character. The character or creature with the highest initiative roll gets their turn first. Then the person with the next highest roll goes, and so on, descending through initiative rolls. When two initiative rolls have the same number, both parties re-roll a d20, without adding their initiative modifier. If there’s another tie, the roll is repeated. Whoever had the higher roll goes before the other person.
	Initiative is generally only mandatory for player characters. The Game Master may roll initiative for each monster individually, all of them as a group, or simply decide when they have their turn instead of the dice.
	On your turn, you can move up to your speed in feet, and take one action. You can break up your movement over the course of your turn- move part of your speed, take your action, and move your remaining speed. You do not need to use all of your movement, or any at all. Things you can use your action for on your turn include:
	Attacking, which involves using your weapon to make an attack roll against an enemy’s Armor Class (AC). Your weapon has an attack modifier which is your strength for melee weapons and dexterity for ranged weapons (unless otherwise noted), as well as your proficiency if it applies. AC is determined by what armor you are wearing, with a score in the armor’s description. Without armor, your AC is usually 10 plus your Dexterity modifier.
	Cast a Spell, which are referred to as Signals in Guardian Project. Most Signals have a casting time of one action, and their effects take place immediately. However, this is not always the case, as indicated by a specific Signal’s description.
	Dash, which effectively doubles your speed for the turn. Using this action, you use your action to move up to your speed.
	Disengage, which means any movement after your action cannot provoke an opportunity attack.
	Dodge, where you focus entirely on dodging attacks. Until your next turn, attacks against you have disadvantage and you make Dexterity saving throws with advantage. These benefits do not apply if you are incapacitated or if your speed is 0.
	Help, where you can aid another creature in a specific task for your turn, giving them advantage on an ability check or attack roll.
	Hide, where you can make a Dexterity (Stealth) check to hide in an appropriate environment, with a DC set by the GM. If successful, any creature trying to find you must make a Wisdom (Perception) check contested by your original roll to hide. Creatures you cannot see have advantage on attack rolls against you, and you have disadvantage on attack rolls against them.
	Ready, used to turn what would be a normal action into a reaction taken when a certain trigger is met.
	Search, where you can make a Wisdom (Perception) check for general searches of the environment or an Intelligence (Investigation) check to look for something specific.
	There are certain character traits, items, and environmental interactions that require an action as well. Most of the time, you only have one action per turn.
	Some traits, Signals, items, and environmental interactions require a bonus action. This is taken in addition to your normal action, and you normally only have one per turn.
	Reactions are not necessarily taken on your turn, but rather in reaction to another creature’s turn. Some character traits and Signals are used in a reaction. There is one type of reaction anyone may take when a creature that was within 5 ft of them moves away from you, which is called an opportunity attack- make a melee attack roll against the fleeing creature. You may only have one reaction per round of combat.
	Successful attacks will deal damage to the target of the attack. There are several different types of dice to roll for damage, depending on what weapon is being used. In addition, each weapon has a damage modifier, usually your strength modifier for melee and your dexterity modifier for ranged. The damage dealt is deducted from the target’s Hit Points. Your own HP is determined at character creation by adding 10 and your Constitution modifier, and scales with level.