For the most part, making attacks in Dungeons & Destiny follows the same rules as making attacks in 5e. There are a few unique rules due to firearms.
Attacking With Firearms
Whether it’s sniping with a linear fusion rifle or providing covering fire with an auto rifle, attacking with a firearm isn’t too different from attacking with a ranged weapon.
Attack and Damage Rolls
When you make an attack with a firearm, you fire an available round from the firearm’s shot capacity (“take a shot” with the firearm). Before determining if your attack hits, subtract 1 shot from your firearm’s shot capacity. If your firearm’s shot capacity is at 0, you must reload it before you can take a shot with it again.
By default, you add your Dexterity modifier to the attack and damage roll of a firearm. If you are proficient with the firearm, you may add your proficiency bonus to the attack roll. You do not add your proficiency bonus to the damage roll of a firearm.
Certain properties on firearms may allow you to use your Strength modifier for the attack and damage rolls instead of your Dexterity modifier, and other properties require the use of your Strength modifier for the attack and damage rolls.
Opportunity Attacks
Unlike traditional ranged weapons, firearms can normally make opportunity attacks. Your firearm’s range band may affect whether or not you have disadvantage on the opportunity attack. Like normal, you can’t make opportunity attacks while Aiming, which many firearms benefit from.
In order to take an opportunity attack with a firearm, a creature must move from being within your controlled space to being outside of your controlled space. For firearms, your controlled space is the space within 5 feet of you. For melee weapons, your controlled space is the reach of the melee weapon. You use your reaction whenever you make an opportunity attack.
If you cannot see a creature, or if a creature teleports, you cannot make an opportunity attack against it.
Payload Weapon Attacks
A special kind of weapon attack, most commonly found on firearms, where the attack consists of firing an explosive or high-yield round with a large impact area. The area of a Payload attack is indicated in parentheses.
When you take a shot with this type of weapon, instead of making an attack roll, choose your impact point, which must be a hard surface within range of the weapon. All targets within the area of the Payload attack must make a saving throw against the weapon’s save DC. The default type of saving throw is Dexterity, but some Payload weapon attacks might specify a different save. Targets take the damage of the weapon on a failed save, or half as much damage on a success.
Weapon Attacks, But Not Attack Rolls. Though you don’t make an attack roll with a Payload weapon, it is still considered to be a weapon attack. In this way, features, traits, weapon perks, and other sources that generally affect weapon attacks also affect Payload weapon attacks. If a source specifically only affects attack rolls, that source would not affect a Payload weapon attack. For instance, a feature that gives you advantage on your next attack roll would not affect your Payload weapon attack.
Advantage and Disadvantage. If, when you take a shot with a Payload weapon, you would normally have disadvantage on the attack, such as when taking a shot against a target within the weapon’s maximum range, your targets have advantage on their Payload saving throw. If you would have advantage on the attack, such as by invoking a feature that grants you advantage on all weapon attacks, your targets have disadvantage on their Payload saving throw.
Automatic Fire With Heavy Weapons Expert
If you make an attack with a weapon that benefits from both the Automatic Fire property and the Heavy Weapons Expert feature, you apply the bonus die provided by Automatic Fire, roll, resolve Heavy Weapons Expert, and finally resolve Automatic Fire.
For example, imagine such a weapon which does 1d6 damage on a hit. First you would roll 2d6. Next, you would reroll either d6 if it rolled as a 1 or a 2 (this resolves Heavy Weapons Expert). Finally, drop the lowest from the total (this resolves Automatic Fire).
On a critical hit with such a weapon, you would roll 3d6, reroll 1s and 2s, then drop the lowest die.
Critical Hits And Misses
Anything that requires an attack roll is able to score critical hits and critical misses. You determine whether you’ve scored one of these by referencing the attack’s critical ranges. By default, an attack’s critical hit range is 20, and its critical miss range is 1. This means you score a critical hit on a roll of 20 on the d20, and a critical miss on a roll of 1.
Critical Hit. When you score a critical hit, you double the amount of all damage dice you roll for the attack’s damage. This includes doubling the number of dice added to the attack, such as the additional dice granted the Empowered condition.
Critical Miss. When you score a critical miss, your attack misses the target regardless of any modifiers you have to your attack roll.
Modifying Critical Ranges. Certain features, traits, perks, or other sources may modify the critical hit or critical miss range of your attack roll. If the critical miss range is increased, you add the next highest number on the d20 to your weapon’s critical miss range. For example, a regular weapon that has its critical miss range increased by one will score a critical miss on a roll of 1 or 2 on the d20, instead of only on a 1. If the critical miss range is decreased, you remove the highest value from the critical miss range.
If the critical hit range is increased, you add the next lowest number on the d20 to your weapon’s critical hit range. This means a regular weapon that has its critical hit range increased by one would score a critical hit on a roll of 19 or 20 on the d20, instead of only on a 20. If the critical hit range is decreased, you remove the lowest value from the critical hit range.
The effect of modifying critical hit ranges can stack across multiple sources. Add them all up to determine your attack roll’s final critical ranges.
Unarmed Strikes
A kick, a punch, a headbutt, or any other melee attack using a part of your body to strike at a target. All creatures are proficient with their unarmed strikes. You use your Strength modifier to determine your attack bonus with an unarmed strike. When you hit with an unarmed strike, you deal an amount of kinetic damage equal to 1 + your Strength modifier.
Wielding Unarmed Strikes
You don’t need to be ‘wielding’ your unarmed strikes to make an unarmed strike. However, if you want your unarmed strikes to be considered melee weapons (and thus benefit from sources that affect melee weapons and melee weapon attacks, such as the Empowered condition), you’ll need to ‘wield’ your capacity for unarmed strikes as a Main-handed weapon. This effectively costs one hand when it comes to the amount of items you can wield. You don’t need to use your hand to make the unarmed strike, but to treat the unarmed strike as a melee weapon, it must be one of your ‘wielded’ items.
‘Drawing’ and ‘stowing’ your unarmed strikes is covered by swap motions (see Drawing, Stowing, and Wielding Items).
Dual-Wielding Weapons
Agile weapons are relatively small and easy to handle, making them ideal for use when fighting with two weapons. If you take the Attack action on your turn and completely resolve the action with attacks from an Agile weapon, you may then use your item interaction to make one additional attack with a different Agile weapon you are already wielding in another hand. This is called making an offhand weapon attack. You do not get to add your ability modifier to the damage of an offhand weapon attack.
Others Sources of Offhand Weapon Attacks
Some perks, traits, features, or other sources may allow you to make an offhand weapon attack in other ways. These offhand weapon attacks don’t necessarily come from an Agile weapon, but they still use your item interaction to do so. Like normal, you do not get to add your ability modifier to the damage of an offhand weapon attack. You may make an offhand weapon attack with a Main- or Two-handed weapon if a perk, class feature, or other source allows you to.