Game Mechanics

= 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.

It deals normal attack damage (the values you see when you select the regular attack as your skill) and this damage can be boosted by physical and elemental charms & gear, Deadly Strike, and Critical Strike.

Skill damage, Crushing blow, Open Wounds, and any other on hit effects will not be applied.

= "Double" damage =

Critical Strike and Deadly Strike have been rebalanced to improve itemization - they now each cap at 75% instead of 100% and multiply damage by 1.5 instead of 2.

There are 4 different types of 1.5x damage stats:
 * Deadly strike: found exclusively on items.
 * Critical Strike: used in the following skills - Critical Strike, Hunger
 * Crit Mastery (melee): used in the following skills - Javelin and Spear Mastery, Claw Mastery, General Mastery, Polearm and Spear Mastery
 * Crit Mastery (throw): used in the following skills - Javelin and Spear Mastery, Throwing Mastery

(An attack is only able to be melee or thrown, therefore only one Crit Mastery type will be taken into account.)

To calculate the chance that one of these stats rolls a crit:

1 - ((1 - MasteryCrit) * (1 - CS) * (1 - DS))

As an example lets take an Amazon with:
 * 30% Crit Mastery from Javelin and Spear Mastery
 * 52% CS from Critical Strike
 * 25% DS from gear

1 - ((1 - .30) * (1 - .52) * (1 - .25)) = ~75% chance to crit

The theoretical maximum combined crit chance is ~96%

= Behavior of -enemy resists =

Breaking immunities
What will break immunities:
 * Battle Cry ( Physical )
 * Poison Creeper ( Poison )
 * Amplify Damage ( Physical )
 * Decrepify ( Physical )
 * Lower Resist ( Fire / Cold / Lightning / Poison )
 * Conviction ( Fire / Cold / Lightning )
 * Static Field ( Lightning )

What will not break immunities:
 * -enemy resistance on gear
 * Cold Mastery
 * Fire Mastery

Enemy resists above 99% (immunes)
Just like in vanilla, the effectiveness of -enemy resistances is reduced when they are applied to enemies who are immune. In vanilla it was reduced to 1/5, but in PD2 this is instead reduced by 1/2. Even after the immunity is broken, immunity breaking skills still only have 1/2 effectiveness.

As an example lets take a enemy with 110 fire resistance, and lets apply a level 20 Lower Resist (-30%) and a level 10 Conviction (-30%).

The correct calculation looks like this:
 * -30 + -30 = -60 [add the two skill values together]
 * -60 / 2 = -30  [apply the 1/2 penalty]
 * 110 - 30 = 80  [take the final -resist value and apply it to the enemy]

It does not work like this:
 * -30 / 2 = -15  [Lower Resist at 1/2 effectiveness]
 * 110 - 15 = 95  [immunity is broken with Lower Resist]
 * 95 - 30 = 65   [apply -resist from Conviction]

It's worth stating again, even after the immunity is broken, immunity breaking skills still only work at 1/2 effectiveness. However this is not the case for -enemy resist on gear, Cold Mastery, and Fire Mastery. While these things are not able to break immunities on their own, they do work at 100% effectiveness after the immunity is broken.

Enemy resists between 0% and 99%
Works identically to vanilla.

Everything works at 100% effectiveness

Enemy resists below 0%
When taking the enemy below 0% resistance you also have to apply the 1/2 penalty. This also applies to gear and items with -enemy resistance.

As an example lets take an enemy with 25 cold resistance, and lets apply a level 20 Lower Resist (-30%) and a level 10 Conviction (-30%):
 * -30 + -30 = -60 [add the two skill values together]
 * 25 - 25 = 0    [the first -25% is reduced at 100% effectiveness]
 * -35 / 2 = -17  [apply the 1/2 penalty to the remaining -35%]
 * 0 - 17 = -17   [final enemy cold resist]

= 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?
 * 1) calculates the number of items to drop (max 6)
 * 2) selects item types
 * 3) selects item qualities
 * 4) selects certain unique or set items (when applicable)
 * 5) 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 drop rate in PD2 is roughly equivalent to /players 5 for solo play, and scales up per player until it's slightly above the equivalent of vanilla's /players 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. In the best case scenario, a TC that was 80% NoDrop in vanilla would be 32% NoDrop in PD2.

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.

Key drop rates
This is a common enough question that it probably makes sense just to show what the drop rates are.

There's very little difference between p1 and p2-p8 so group key farming isn't really necessary.