Speed is an inherent property of all creatures in ADOM (including the PC) that determines how quickly and in what order they make take actions.
How Speed Works
Every action in ADOM has an associated energy cost to it. This energy cost determines how long it takes for that action to be performed--or, more accurately, how quickly the actor may recover after the action has been performed (since the action itself otherwise is instantaneous). Most common actions such as walking and attacking have an energy cost of 1000. Speed determines the rate at which the actors restore their energy--the more speed that the player has, the faster that they may act. On the simplest level, if one actor has 100 speed and another has 120, then the one with 120 speed will be able to act 6 times for every 5 that the one with 100 speed does. Things get more complicated when energy cost is taken into account, however. Seven league boots, for example, can reduce the energy cost of walking from 1000 to 750. If the actor with 100 speed was then wearing seven league boots, they could walk 5 steps for every 3 the actor with 120 speed would take.
While players have a means to monitor the cost of their actions, there are no easy means to monitor the energy cost of the actions of monsters. The manual and some testing seem to strongly suggest that the vast majority of monster actions require exactly 1000 energy; however, this is offset by the fact that many monsters may attack multiple times per turn, whereas the player can normally only attack once. There has been some spectulation that certain monsters (eg. the Cat lord) may have lower energy movement, however. In general though, this simplifies the analysis considerably since all that would be required to determine if, eg. the player can outrun a monster, is to simply compare their speeds--if the monster has a lower speed than the PC, then the PC should be able to outrun the monster, so long as their base movement energy is 1000 or less.
Speed is also known to have an effect on the player's ability to dodge magical bolts and missile attacks. The exact relation has not yet been quantified.
Effect on Experience
Speed is a very desirable attribute. Even small increases in speed can have significant effects on the dynamics of combat, and may allow extra turns or determine whether or not the player can safely flee from combat. The downside is that speed has a direct effect on the experience that the player receives--there is an experience penalty for killing something slower than the PC, and an experience gain for killing something that is faster.
JellySlayer performed an experiment relating monster speed to player speed, and found that the relation between the two is:
In other words, a player with the Raven starsign (ie. 110 base speed) who kills a monster with 100 speed will receive only 91% of the experience points for that monster. For low speeds, this effect is not that substantial--an difference of 2 speed results in only a 2% penalty--if the difference is large, then the penalty can be severe: at a 100 speed difference, the player only receives half the available experience. On the other hand, this can be exploited: being strained and bloated will reduce the PC's speed by 20, whic this yields a 25% increase in experience against monsters with 100 speed—with, of course, increased risk in combat.
Because of the effect on experience, many players often manipulate their speed in order to maximize experience gains while minimizing risk. The easiest way to do this is encumbrance: being burdened reduces speed by 5, strained by 10, and strained! by 20. Simply by carrying around stacks of disposable items, such as large rations or huge rocks, the player can maintain a small but persistent experience bonus--and then abandon these items if they need to make a quick escape. The Slow Monster spell is often used to similar effect: the experience bonus is only calculated when the monster is killed, thus many players, while fighting a difficult monster, will cast Slow Monster on themselves when the monster is critically wounded, and then kill the monster with 50% of their base speed. This results in a massive increase in experience for, again, relatively minimal risk.
The benefits of high speed should not be understated, however: the ability to move much faster than your opponents is significant, and, particularly since the energy cost of attacking decreases with weapon skill, with relatively modest speed values, it is possible to attack two or more times for every one that the opponent receives. In particular, players intending to pursue Ultra Endings often want speeds significantly above 100 to ensure a victory.
Common Ways to Modify Speed
|Slowed (Slow Monster, or by an opponent)||-50%|
|Cold blood corruption||-10|
|Bloody sweat corruption||+5|
|Talents (Quick, Very Quick, Greased Lightning)||+2, +3, +4 for 9 total|
|Athletics Skill||up to +8|
|Dexterity||+1 for every 2 points above 17|
|Very light corruption||+20|
|Wish (temporary only)||+100-200|
Monks and beastfighters also receive speed bonuses as they level. Some items such as a quicksilver quarterstaff, ring of speed, or boots of the slow shuffle and the artifacts black torc, Ring of the Master Cat and Boots of Great Speed can also impact the PC's speed. Corpses of monster such as quicklings and claw bugs, and potions of quickling blood, can also increase base speed. The Devour order corruption grants a temporary 1d100 speed boost every time the PC eats the corpse of a lawful monster.
Age gradually reduce Speed.