To hit (short for 'chance to hit') is the probability that an attack will hit a target. It is one of the two key factors in determining the success of an attack, the other being damage.
The to hit can be calculated for melee and ranged attacks, and is calculated differently for players and monsters. The largest factors for players are weapon (or unarmed) skill and fighting skill - with good training on both skills and decent dexterity, it should be rare to miss most targets.
Player To Hit (Melee and Ranged)
The player's to-hit in melee and ranged combat is determined by the following factors:
- Start with 15 + dexterity/2 + a random roll between 0 and your fighting skill.
- Add a random roll from 0 to your weapon skill (unarmed is considered a weapon skill here).
- Add the weapon's base accuracy; unarmed has +2, or +4 if you have claws.
- Add your weapon enchantment level and slaying bonuses.
- If in wisp, fungus, pig, or non-vampire bat form, add random2(XL*100+100)/100 instead of using your weapon skill above.
- Subtract 5 for vertigo.
- If you have the eyeballs mutation, add 2*[eyeballs level]+1.
- Take this total and roll a random number from 0 to (total - 1).
- Subtract 5 from wearing the Amulet of the Air.
- Subtract 5 if missing an eye (Ru sacrifice) or you are confused.
- Subtract 6 if you cannot see the target (invisibility).
- Add 2 + roll between 0 and 7 if the target is backlit (Corona, Sticky Flame, or under a halo).
- Subtract 2 + roll between 0 and 3 if the target is in umbra and you do not have night vision (from Dithmenos & Yredelemnul).
- The Confusing Touch spell grants +0 to +(DEX-1).
Monster To Hit (Melee)
A monster's to hit is calculated as follows:
The base value is 18.
Monsters with the Fighter class flag get a bonus of +(2.5 * HD). Other monsters get +(1.5 * HD). Decimals are rounded down.
- An aquatic monster "using the terrain to its advantage" gets +5.
- A monster wielding a weapon receives that weapon's inherent and magical to hit modifiers.
- A confused monster gets -5.
- A monster attacking a backlit defender gets +2 to +9.
- A monster attacking an invisible target suffers a 35% penalty to its to hit number.
Monster To Hit (Ranged)
Ranged attacks ("beams", to use the game's internal terminology) have a to hit number, just like melee attacks do. This is modified as follows:
- If you are invisible and the attacker can't see invisible, the to hit number is halved.
- If you have Repel Missiles, the to hit number is reduced by a random number between 0 and 1/2 of its value (rounded down).