Unarmed Combat

The Unarmed Combat skill determines the effectiveness of all attacks made with your character's fists (or tentacles in the case of octopodes), increasing the damage, accuracy, and speed of your unarmed attacks. Although there are many non-punch auxiliary attacks you can make with the rest of your body, these are not affected by the UC skill whatsoever. Training this skill is only advisable if you intend to engage in melee while unarmed or while leaving your off-hand empty.

For many species, fighting without a weapon is not a very appealing prospect. Leaving your weapon and/or shield slot open means that you cannot take advantage of weapon brands, miss out on the defensive value of a shield, and have two fewer slots for wielding artifacts that may provide useful resistances or other bonuses. However, unarmed combat allows for some of the fastest attacks in the game, deals competitive damage to weapon wielders at high skill levels, and allows you to take advantage of the many Transmutations spells which grant you powerful unarmed capabilities. Also, some species have natural aptitudes or innate mutations that make unarmed combat a much more tempting choice.

Attack Delay

Unarmed combat specialists are capable of making some of the fastest attacks in the game, on par with the speed of most short blades wielders. Couple this with the fact that UC attacks have a much higher base damage than any short blade, and you can see why they're capable of doing very significant amounts of damage very quickly. However, it requires much more Unarmed Combat skill to reach maximum attack speed than it does for a weapon fighter to reach their maximum, and unarmed combat is penalized for wearing heavy armour or carrying too much equipment. Bear in mind that this only applies to main-hand punches; auxiliary offhand punches occur along with your main hand attacks.

Bonuses From Skill

Weapon fighters gain a 1 point reduction to their attack delay for every 2 levels they have in their appropriate weapon skill, allowing them to reach maximum weapon speed by the mid-game in most cases. Unarmed Combat uses a different formula, however; your attack delay is reduced by 1 for roughly every 5.4 skill levels, reaching a delay of 5 at UC skill 27. Fortunately, unarmed combat is also much faster than fighting with most weapons by default, so they still enjoy fairly quick attacks throughout the game.

EV Penalties

Wearing barding, a shield, or armour with any EV penalty may increase your UC attack delay. Every time you throw a punch, the following die roll is made for each piece of equipment:

1d10 + 2d(EV Penalty) - 10

If the result of this roll comes out positive, the attack's delay is increased by the item's EV penalty. While the penalties for wearing a buckler or leather armour are fairly minimal, any of the heavier armours might prove a bit more difficult to fight effectively in. Still, many trolls win the game using gold dragon armour and a large shield in order to make up for their poor defenses, and it's not rare for other unarmed fighters to use a large shield, sacrificing some damage output for excellent melee defense.

Encumbered

Fighting while encumbered or overloaded negates any bonus to attack delay you may receive from your unarmed combat skill. Penalties from your EV penalty still apply.

Other Factors

Characters in bat form receive a special bonus to unarmed combat, making attacks in 60% of the normal time (though at a significant penalty to damage). Other effects that can influence attack speed (such as Haste, Slow, Statue Form, etc.) apply as normal, with a hardcoded limit at 3 which you cannot exceed.

Final Calculation

Finally, your attack delay can never be a fraction of a turn. If your calculated speed falls between two whole numbers, the game will round up or down based on the remainder (7.2 would have a 20% chance of being rounded to 8 and an 80% chance of being 7).

UC	Avg delay	UC	Avg delay	UC	Avg delay
0	10.0	10	8.1	20	6.3
1	9.8	11	8.0	21	6.1
2	9.6	12	7.8	22	5.9
3	9.5	13	7.6	23	5.7
4	9.2	14	7.4	24	5.6
5	9.1	15	7.2	25	5.4
6	8.9	16	7.0	26	5.2
7	8.7	17	6.8	27	5.0
8	8.5	18	6.7
9	8.3	19	6.5

Base Damage

The base damage of your primary unarmed combat attack is determined through the following factors:

Condition	Damage	Special
Bat Form	1	60% Attack Delay
Vampire Bat Form	2	60% Attack delay
Spider Form	5	Venom
Ice Form	12	Freezing
Blade Hands	12 + (STR + DEX) / 4	-
Statue Form	9 + STR / 2	150% attack delay
Dragon Form	12 + (2/3) STR	Heavy bleeding
Lich Form	5	Draining
Troll	9	Heavy bleeding
Ghoul, Felid	5	Light bleeding
Octopode, Naga	3	Constriction
Claws mutation	+2 × Claws ranks	Wearing gloves negates this
Other	3	-

Your base damage is then increased by your unarmed combat skill level (divided by 5 when in Bat Form). This base damage is then further modified by your strength, dexterity, Fighting skill, and other factors. A value is randomly selected between 1 and the final calculated damage, and the target's AC is applied against it.

Offhand punches are significantly less powerful, using the following calculation:

Condition	Damage	Special
Offhand Punch	5 + (UC / 3) +(1d3 × Claws ranks) or +(6 if Blade Hands)	Wearing any shield negates this

History

In earlier versions of Crawl, Unarmed Combat improved the performance of your non-punch auxiliary attacks, giving all melee fighters a reason to train it.

Unarmed Combat Aptitudes

From Dungeon Crawl Stone Soup 0.11.0 in-game documentation:

Hu	Ce	Dg	Ds	Dr	DD	DE	HE	SE	Fe	Gh	Ha	Ko	Mf	Mi	Mu	Na	Op	Og	HO	Sp	Te	Tr	Vp
0	0	-1	-1	0	-1	-2	-2	1	0	1	-2	0	1	1	-2	0	0	-1	1	-2	1	0	1