Game Mechanics

== General ==
* Oskills are skills without a class-specific modifier, such as "+X to Battle Orders" or "+X to Zeal", and are limited to +3 from all sources when used on the class the skill belongs to. For example, the Ferocity runeword on a paladin will provide +3 to Zeal rather than the listed +12 to +14. This is a regular D2 mechanic.
== Melee Splash ==
Melee splash is an instant AoE, with no Next Hit Delay, that damages all enemies 360° around the target. The main target does not take splash damage.	
An attack's splash damage is rolled once and applied according to each enemy's resistances, but effects that have a chance of applying (Crushing Blow, Open Wounds) are rolled individually for each enemy hit in melee splash.
These are included in the splash:
* Skill damage
* Converted damage (e.g. Concentrate)
* Normal attack damage (the values you see when you select the basic attack as your skill)
* Elemental and physical damage from charms and gear
* Critical Strike and Deadly Strike (still only applies to the physical damage)
* Life and Mana leech (reduced by 1/2, and still only applies to the physical portion of the attack)
* Crushing Blow
* Open Wounds
These are not included in the splash:
* Missile damage (such as the Nova portion of Power Strike)
* Stun
* Knockback
* Any other on-hit effects
=== Melee Splash Examples ===
Let's take a look at a couple of examples. First, let's take an Amazon:
* Lightning Strike for 1-10000 lightning damage and 1-10000 chain lightning damage
* Normal attack damage of 1000-5000 (900-4900 of that is physical)
The total splash damage would be 1001-15000 damage. 
And if they crit then the splash damage would be 1451-17450. 
The 1-10000 damage from the Chain Lightning is not applied.
What about a Barbarian:
* Concentrate (300% ED, 50% conversion)
* Normal attack damage of 1000-5000 (900-4900 of that is physical)
First the physical portion of the normal attack damage is boosted by Concentrate's ED% bonus: 900-4900 becomes ~1800-9800
Then 50% of the physical damage is converted to magic
The total splash damage would be 1900-9900 [100-100 elemental damage + 900-4900 physical + 900-4900 magic]
And if they crit then the splash damage would be 2800-14800
=== Splash Radius ===
The base player melee splash radius is 5 tiles (3.33 yards) but this can be extended by certain skills and items. The splash radius will increase by 1 tile (0.66 yards) for every 20% "increased splash radius" gained.
Increased Splash Radius	0 	20	40 	60
Tiles 	5 	6 	7 	8
Radius (yards) 	3.33	4 	4.66	5.33
There are also a handful of other things that have melee splash. These are all static and cannot be increased.
* "Splashing" map modifier: melee splash radius is 5 tiles (3.33 yards)
* Golems: melee splash radius is 4 tiles (2.66 yards)
* Skeletons: melee splash radius is 3 tiles (2 yards)
* Wolves: melee splash radius is 2 tiles (1.33 yards)
=== Melee splash and ranged weapons ===
There are a few gloves (The Hand of Broc, Bloodfist, and Steelrend) that have melee splash on them and they can be used to give ranged weapons, like bows and crossbows, melee splash.
This allows shapeshifters to use a ranged weapon in place of a melee weapon, while still gaining the benefits of melee splash.
This does not mean that ranged attacks (i.e. shooting with a bow) will have splash damage. Melee splash is always limited to melee attacks.
== Critical Damage ==
Critical damage has been rebalanced to improve itemization by making the power of Deadly Strike more comparable to other item stats, and other sources of crit chance have been changed in the same way. Skills have been rebalanced with additional damage to compensate for this difference.
Each source of crit chance now caps at 75% instead of 100% and crits multiply physical attack damage by 1.5x instead of by 2x. In Season 10 a new stat "+x% maximum deadly strike" on items such as Wraithskin, Death Cleaver and Headstriker was introduced. This means that one can now have 100% chance to deal critical damage by stacking these items.
There are 3 different sources of crit chance:
* Deadly Strike: items, Blessed Aim
* Critical Strike: Critical Strike, Joust
* Weapon Mastery: General Mastery, Polearm and Spear Mastery, Throwing Mastery, Claw and Dagger Mastery, Javelin and Spear Mastery
Total Crit Chance: 1 - ((1 - DS) * (1 - CS) * (1 - WM)) (rounded down to the nearest percent)
: As an example, consider an Amazon with:
:* 50% DS crit from gear
:* 50% CS crit from Critical Strike
:: 1 - ((1 - 0.50) * (1 - 0.50) * (1 - 0)) = 75% chance to crit
: Another example:
:* 40% DS crit from gear
:* 65% CS crit from Critical Strike
:* 30% WM crit from Javelin and Spear Mastery
:: 1 - ((1 - 0.40) * (1 - 0.65) * (1 - 0.30)) = 85% chance to crit
The theoretical maximum total crit chance is 95% (75% DS, 75% CS, 35% WM)
== Life and Mana Steal ==
=== Leech Reductions ===
Attack leech reduction
* Melee Splash: 1/2 [Life/Mana]
* Ranged Attacks: 1/2 [Life/Mana]
Skill leech reduction
* Blade Shield: 1/2 [Life/Mana]
* Leap Attack: 1/3 [Life]
Difficulty leech reduction
* Normal: N/A
* Nightmare: 1/2 [Life/Mana]
* Hell: 1/3 [Life/Mana]
Zone leech reduction
* PvP maps: set leech to 0% [Life/Mana]
=== Leech Formula ===
leeched life/mana = [[[leech * attack_reduction * skill_reduction] * 64 * difficulty_reduction] * physical_damage * drain_effectiveness / 64 / 100]
Note: Bracketed values are rounded down
As an example, consider a Barbarian with 7% Life leech, using Leap Attack (5k damage) against The Cow Queen:
* [[[7 * 1/2 * 1/3] * 64 * 1/3] * 5000 * 0.2 / 64 / 100]
* [[1 * 64 * 1/3] * 5000 * 0.2 / 64 / 100]
* [21 * 5000 * 0.2 / 64 / 100] = 3hp leeched
Another example, consider a Paladin with 9% Life leech, using Zeal (3k damage) against a Death Beatle:
* [[[9 * 1/2] * 64 * 1/3] * 3000 * 0.5 / 64 / 100]
* [[4 * 64 * 1/3] * 3000 * 0.5 / 64 / 100]
* [85 * 3000 * 0.5 / 64 / 100] = 19hp leeched
== Crushing Blow ==
Crushing Blow reduces the target's life by a fraction of their current life, so it's more effective against targets with lots of life and becomes less effective as they lose life. Attacks can have up to 100% chance to cause a Crushing Blow - any extra will have no effect.
* Crushing Blow now has greater diminishing returns against bosses (act bosses, map bosses, ubers)
* The melee life reduction is now the same as the ranged reduction
Target 	Melee(PD2)	Ranged(PD2)	Melee(LoD)	Ranged(LoD)
Most Targets 	1/8 	1/8 	1/4 	1/8
Super Uniques 	1/8 	1/8 	1/8 	1/16
Bosses 	1/80** 	1/80** 	1/8 	1/16
Players and Mercenaries	1/10 	1/10 	1/10 	1/20
* "Most Targets" refers to pets as well as normal, minion, Champion, and Unique monsters
** Affected by diminishing returns: 80 + pow(missing hp%, 2)
Also see: Vanilla Info about Crushing Blow
== Open Wounds ==
* Open Wounds deals physical damage over time
** The damage depends on the level of the character who applies it (shown below for all levels)
** The damage is now affected by "+X Open Wounds Damage per Second" which is a new attribute that often accompanies "X% Chance of Open Wounds"
** The damage is now affected by Physical Damage Reduction (e.g. Battle Cry, Amplify Damage, Defiance, etc)
** The damage is not affected by other damage modifiers
* Open Wounds is now also applied by "Attacker Takes Damage of X" as well as attacks
* Open Wounds now lasts 5 seconds (was 8 seconds) and now stacks up to 3 times per target
* Open Wounds now has a ¼ penalty against mercenaries and pets
* Open Wounds no longer has a ½ penalty against stronger enemies (champions, uniques, super uniques, bosses, prime evils)
 Open Wounds Damage per Second
Character Level 	1 	2 	3 	4 	5 	6 	7 	8 	9 	10 	11 	12 	13 	14 	15 	16 	17 	18 	19 	20 	21 	22 	23 	24 	25
Damage per Second	3 	4 	5 	6 	7 	8 	9 	10 	10 	11 	12 	13 	14 	15 	16 	17 	19 	21 	23 	25 	26 	28 	30 	32 	33
 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	
Character Level 	26 	27 	28 	29 	30 	31 	32 	33 	34 	35 	36 	37 	38 	39 	40 	41 	42 	43 	44 	45 	46 	47 	48 	49 	50
Damage per Second	35 	37 	39 	40 	42 	45 	47 	50 	53 	55 	58 	61 	63 	66 	68 	71 	74 	76 	79 	82 	85 	89 	92 	96 	99
 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	
Character Level 	51 	52 	53 	54 	55 	56 	57 	58 	59 	60 	61 	62 	63 	64 	65 	66 	67 	68 	69 	70 	71 	72 	73 	74 	75
Damage per Second	103	106	110	113	117	120	124	127	131	134	139	143	148	152	156	161	165	170	174	178	183	187	191	196	200
 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	
Character Level 	76 	77 	78 	79 	80 	81 	82 	83 	84 	85 	86 	87 	88 	89 	90 	91 	92 	93 	94 	95 	96 	97 	98 	99 	
Damage per Second	205	209	213	218	222	227	231	235	240	244	249	253	257	262	266	271	275	279	284	288	293	297	301	306	
Also see: Vanilla Info about Open Wounds, Deep Wounds
== Reducing Resistances ==
Resistances are now reduced at 1/2 effectiveness (was 1/5 effectiveness) when those resistances are above 99% (immunes) or below 0%.
This effectiveness penalty only applies to effects caused by players and pets. Negative resistances caused by monsters (e.g. Conviction, Amplify Damage) are always applied at full effectiveness.
=== Breaking Immunes ===
These effects "reduce" or "lower" enemy resistances and will break immunities. They all apply an effect to the enemy which persists and reduces their resistance while it is active, which allows all players to benefit:
* Battle Cry (Physical)
* Amplify Damage (Physical)
* Decrepify (Physical)
* Lower Resist (Fire/Cold/Lightning/Poison)
* Conviction (Fire/Cold/Lightning)
* Sanctuary (Magic)
* Poison Creeper (Poison)
* Arctic Blast (Cold)
* Inferno (Fire)
* Static Field (Lightning)
These effects "penetrate" or "pierce" enemy resistances and will not break immunities. They only benefit the character who uses them:
* -% to enemy resistance from items or skills (e.g. Kira's Guardian, Rainbow Facet, Cold Mastery, Fire Mastery, Poison Strike, Berserk)
=== Effectiveness vs Immunes ===
All effects which "reduce" resistances (those that can break immunities) are applied simultaneously against immune enemies, rather than sequentially. This means that even if multiple immunity-breaking skills are used and one of them would be powerful enough to break an immunity alone, they all still apply at 1/2 effectiveness.
: As an example let's take an enemy with 110% fire resistance, and apply both Lower Resist and Conviction each at levels where they have "Enemy Resistances -30%":
:* -30 / 2 = -15  [apply the 1/2 penalty to Lower Resist]
:* -30 / 2 = -15  [apply the 1/2 penalty to Conviction]
:* 110 - 15 - 15 = 80  [take the final -resist values and apply them to the enemy]
Effects which "penetrate" resistances rather than "reduce" them (e.g. Rainbow Facet, Cold Mastery) will be applied afterward and will work at full effectiveness against enemies that have had their immunities broken. 
=== Effectiveness vs Negative Resistance ===
When taking an enemy below 0% resistance, the effectiveness penalty only applies to whatever portion becomes negative. Everything applies at full effectiveness and then afterward, if the enemy's resistance is negative, it gets halved.
: As an example let's take an enemy with 25% cold resistance, and apply Lower Resist and Conviction from before as well as an extra "-12% to Enemy Cold Resistance":
:* 25 - 30 = -5  [Lower Resist]
:* -5 - 30 = -35  [Conviction]
:* -35 - 12 = -47  [-Enemy Resist]
:* -47 / 2 = -23  [apply the 1/2 penalty to get the final enemy cold resist]
Resists can be reduced as low as -100%
== Item drop mechanics ==
=== Item drop Basics ===
Lets look at a high-level example of how the drop process works.
Mephisto is killed! What does the game do to determine your reward?
# calculates the number of items to drop (max 6)
# selects item types
# selects item qualities
# selects certain unique or set items (when applicable)
# selects item properties (when applicable)
The number of players only affects item #1, the number of potential drops. It has no affect on the quality of the items that drop (this is where magic find comes into play). Now the question is, how does the number of players affect how many items drop?
Any time you do something that drops loot (opening a chest, killing a monster, etc.) the game selects from a list of treasure classes (TC) that will decide what kind of items will drop. Each TC has a list of items (or other TCs) that can drop, as well as a probability that that given item will drop. There is also a number of "picks" for each TC that decides how many potential items can drop. The last piece of the puzzle is "NoDrop", which is a probability that a pick will drop no items. NoDrop is the only parameter that player count affects.
There's a lot that goes into how the new NoDrop value is calculated when more players join the game, but the short version is: the higher the player count, the lower the NoDrop chance (potentially reaching 0 with enough players). 
There are some TCs that start with NoDrop at 0. These are not affected by player count, since 0 is the lowest possible value.
=== What's different in PD2? ===
The baseline drop rate in PD2 is roughly equivalent to vanilla's p5/5 (5 partied players in a game) for solo play, and scales up per player until it's slightly above the equivalent of vanilla's p8/8 when there is a full game of 8 players. This means that overall NoDrop for all TCs is significantly lower, and it becomes easier to reach a NoDrop of 0 with fewer players.
You still get loot increases from more players like vanilla, but the difference between a solo player and a group of 8 is overall much smaller.
Rune TCs are also the same as in vanilla, so rune drop rates are the same. Miniscule differences may exist in some cases due to new valuable items such as Larzuk's Puzzlebox being able to drop.
=== How does PD2 compare to LoD? ===
It's hard to directly compare the two since there are hundreds of TCs, and PD2 has even more than LoD (mostly because of maps). But we can compare a TC from LoD to a TC from PD2 and see how the NoDrop chance has changed.
Let's look at the TCs called Swarm 2 (H), a worst case scenario, and Act 2 (H) H2H A, a common case used by many monsters. In these examples, the first number is the amount of players in the game and the second number is the amount of players in the party. So p3/2 means 3 players in the game but only 2 in your party. If you used the /players 8 command in single player that would be equivalent to p8/1.
Chance for NoDrop to be selected by the "pick" (i.e. the chance that no item drops):
Treasure Class 	LoD	PD2
Swarm 2 (H) 	
* p1/1, p2/1 = 83.33%
* p2/2, p3/1, p3/2, p4/1 = 69.14%
* p3/3, p4/2, p4/3, p5/1, p5/2, p6/1 = 57.63%
* p4/4, p5/3, p5/4, p6/2, p6/3, p7/1, p7/2, p8/1 = 47.92%
* p5/5, p6/4, p6/5, p7/3, p7/4, p8/2, p8/3 = 39.02%
* p6/6, p7/5, p7/6, p8/4, p8/5 = 32.43%
* p7/7, p8/6, p8/7 = 26.47%
* p8/8 = 21.88%	
* p1/1, p2/1 = 40.85%
* p2/2, p3/1, p3/2, p4/1 = 16.64%
* p3/3, p4/2, p4/3, p5/1, p5/2, p6/1 = 6.68%
* p4/4, p5/3, p5/4, p6/2, p6/3, p7/1, p7/2, p8/1 = 2.75%
* p5/5, p6/4, p6/5, p7/3, p7/4, p8/2, p8/3 = 0.99%
* p6/6, p7/5, p7/6, p8/4, p8/5 = 0.33%
* p7/7, p8/6, p8/7 = 0.17%
* p8/8 = 0%
Act 2 (H) H2H A	
* p1/1, p2/1 = 62.50%
* p2/2, p3/1, p3/2, p4/1 = 38.78%
* p3/3, p4/2, p4/3, p5/1, p5/2, p6/1 = 24.05%
* p4/4, p5/3, p5/4, p6/2, p6/3, p7/1, p7/2, p8/1 = 14.29%
* p5/5, p6/4, p6/5, p7/3, p7/4, p8/2, p8/3 = 9.09%
* p6/6, p7/5, p7/6, p8/4, p8/5 = 4.76%
* p7/7, p8/6, p8/7 = 3.23%
* p8/8 = 1.64%	
* p1/1, p2/1 = 9.52%
* p2/2, p3/1, p3/2, p4/1 = 0.88%
* p3/3, p4/2, p4/3, p5/1, p5/2, p6/1 = 0%
* p4/4, p5/3, p5/4, p6/2, p6/3, p7/1, p7/2, p8/1 = 0%
* p5/5, p6/4, p6/5, p7/3, p7/4, p8/2, p8/3 = 0%
* p6/6, p7/5, p7/6, p8/4, p8/5 = 0%
* p7/7, p8/6, p8/7 = 0%
* p8/8 = 0%
=== Key drop rates ===
Players 	1 	2 	3 	4 	5 	6 	7 	8
Blood Raven 	12.127%	12.161%	12.161%	12.161%	12.161%	12.161%	12.161%	12.161%
Countess 	7.350% 	6.274% 	5.906% 	5.906% 	5.906% 	5.906% 	5.906% 	5.906%
Bloodwitch 	12.127%	12.161%	12.161%	12.161%	12.161%	12.161%	12.161%	12.161%
Summoner 	13.541%	13.595%	13.595%	13.595%	13.595%	13.595%	13.595%	13.595%
Izual 	12.127%	12.161%	12.161%	12.161%	12.161%	12.161%	12.161%	12.161%
Nihlathak 	12.618%	12.645%	12.645%	12.645%	12.645%	12.645%	12.645%	12.645%
 	 	 	 	 	 	 	 	
Countess (LoD) 	7.353% 	9.434% 	10.000%	10.204%	10.204%	10.204%	10.204%	10.204%
Summoner (LoD)	8.929% 	12.195%	13.158%	13.514%	13.514%	13.514%	13.514%	13.514%
Nihlathak (LoD) 	8.197% 	10.870%	11.628%	11.905%	11.905%	11.905%	11.905%	11.905%