DV stands for Defensive Value and is the first value displayed in the bottom left corner, the second being PV. It is the value used in calculations of whether an enemy attack will hit you - the higher your DV, the harder to hit will your character be. DV is influenced by many factors, including but not limited to: your race, class, Dexterity, Alertness, satiation level, burden level, corruptions, weapon skill, tactics setting, the presence of the Dodge skill, shield and shield skill, and armor and equipment in general. Being a Monk will grant a significant DV bonus dependent on the character level, provided the character does not wear too heavy body armor or wield a shield. Talents can also provide points of DV. On equipment, the DV modifier is always the first value displayed in square brackets. For instance, a standard issue small shield will be displayed as "small shield [+2, +0]", and will provide you with two extra points of DV. More specifically:
- Weapon skills, full bonus for weapon in right hand, half bonus for weapon in left hand, up to 2 * (highest equipped shield DV) from shield skill
- Duelist class power, +2*Wep Skill
- Dexterity 13+, +1 per 2 points
- Monk class ability, +2/3*PC level
- Beastfighter class ability, +1/3*PC level
- Initial DV, +10
- Dodge skill, up to +10
- Fighter/Assassin Dodge skill bonus, up to +10/+20
- Shield Specialist talent and its successors when equipped with shield, +1/+2/+3
- Careful/Defensive Fighter/Dodger talents, +1/+2/+2
- Satiated, Bloated satiation levels, -1/-3
- negative corruptions: Bronze Bones, Rage, -2/-9
- positive corruptions: Thin and nimble, Unholy aura, +6/+6
- Burden levels, -1 per level
- Drunk condition, -3
- Mental shield, +(W + CL)/5
- Alertness skill, up to +4
- Tactics, up to +60%
- of defense weapon suffix +6
Most regular body armor will not give DV bonuses, and heavier armor, while it will provide more PV, will tend to lower your DV value; in the early game, this is a worthwhile trade, as each single point of PV is worth much more than a point of DV. Later on, a shield may provide for a substantial amount of your total DV.
Note that DV can be "too high" in that higher scores of DV will stop providing benefits. Testing seems to suggest that even with excessively high DV, monsters seem to hit at a rate of around 1 in 12. This may be reduced if the PC has the lucky or Fate Smiles intrinsics, and increased if the PC is Cursed or Doomed. These conditions are generally believed to tamper with dice rolls, so the negative or positive effect likely has to do with making several rolls and using the more (or less) beneficial one.
For most monsters against an undoomed PC, this limit seems to be achievable with around 80-100 DV. For extremely experienced foes (which presumably have higher to-hit), this may not be enough, however.
This might be related to the Dungeons & Dragons origins of ADOM; the equivalent of DV, AC, does not provide additional benefits upon increasing if it already exceeds the monster's attack bonus by 20 points - monsters will always hit on a roll of 20 on their d20, regardless of the AC of the player. Similar mechanics might be at work in ADOM, causing the "1 in 12" phenomenon and giving weaker monsters a chance to hit the player.
Another thing to note is that from rough observations DV can be divided into three "groups":
- "Base DV" is DV that comes with the character's Dexterity score, plus the DV granted by pieces of armor, such as cloaks.
- "Dodge DV" is DV that is granted by the Dodge skill. It is special because the Dodge skill is only trained (and thus given higher trainable maximums during skill increases) if a hit is avoided thanks to Dodge, i.e. a monster rolled enough to have hit versus only Base DV, but does not versus Base DV plus Dodge DV. Dodged attacks still "miss" as per in-game messages.
- "Shield DV" is the third group, and represents the bonus granted by shields and the shield skill. It is the third value added to determine if and how an attack is defeated; if the attack would beat both Base and Dodge DV (if present), but does not beat the total DV with shield added in, it is "deflected" or "blocked" instead of hitting. Only then are shield marks trained.
This has consequences for training both Dodge and the shield skill, obviously. First of all, Dodge is very hard to train if it is low, except in the early game in which characters start with substantial trainable maximum, since monsters have to roll very exact values for it to be trained. A high Base DV will also make it somewhat harder for Dodge to increase, since it will tend to leave fewer monsters capable of rolling within the Dodge range. Shields do not technically impede Dodge training at all; a blocked attack would not have trained Dodge with or without a shield.