Core:Attack Interaction

The most important interaction is the attack interaction, which is used whenever a weapon, body part, or missile would come into contact with a target. The Attacker first makes an attack roll (1d20) against the target's armor class (AC). If the attacker is proficient with the ability they are using, they add their proficiency bonus (P) to the roll. If this roll is equal to or greater than the target's AC (typically 10 + AV), the attack hits. If the roll is less than the target's AC, the attack misses. A natural 20 on the die is always a hit, and a natural 1 is always a miss. The consequence of a hit is described in the "On hit" section of the ability that's used.

If the hit is from a natural 20, then the attack is a critical hit and the effect of the ability "goes critical". If this changes anything about the effect, then it's described in the ability's "On critical hit" section. Any creature that is up may choose to be hit by an attack, even if the attack would normally miss. This is called "Taking the hit". They cannot choose to take a critical hit.

Multiple Attacks

Attacks are always associated with a hand. This could be the hand that uses a weapon, that casts a spell, or that performs an unarmed strike. The first attack you make with a given hand has no penalty to hit. Each subsequent attack you make with that hand in the same turn incurs a cumulative -3 attack penalty to hit. Your attack penalty resets to 0 at the end of your turn.

Lord Goobelthorp is wielding a claymore in two hands. The first attack they make with the claymore has no penalty to hit. If they make a second attack with the claymore in the same turn, that attack incurs a -3 penalty to hit. If they make a third attack with the claymore in the same turn, that attack incurs a -6 penalty to hit.

Kaflimbo is wielding a shortsword in each hand. The first attack they make with one of the shortswords has no penalty to hit. If they make a second attack with their other shortsword in the same turn, that attack also has no penalty to hit. If they make a third attack with one of the shortswords in the same turn, that attack incurs a -3 penalty to hit.

Tizzy Snomblom has a war hammer in one hand and a tower shield in the other. The arm with the tower shield is also holding a dagger, although they cannot attack with it. The first attack they make with the hammer has no penalty to hit. If they make a second attack with the hammer in the same turn, that attack incurs a -3 penalty to hit. If they make a third attack with the hammer in the same turn, that attack incurs a -6 penalty to hit.

Flaxer Gogo has a longsword in one hand, a dagger in the other, and a buckler shield strapped to the arm with their dagger. The first attack they make with the longsword has no penalty to hit. Since they're using is buckler shield (and not some larger type of shield), they can also make a second attack with the dagger in the same turn without incurring a penalty to hit. If they make a third attack with the longsword or the dagger in the same turn, that attack incurs a -3 penalty to hit.