Luck

From Arcanum

Luck has a minor effect on several things:

  • It increases the rate at which loot is dropped.
  • It gives a chance for a 5% heal ("has a close call") when you die (retreat) in combat.
  • It increases the likelihood of getting a benefit from actions that have a % chance to give you something, such as the Concoct Potions action.

Math

The chance of getting a 5% heal when you die in combat is (luck)%.

The chance of getting a benefit from actions that have a % chance of something is multiplied by (100+luck)/100.

Monster loot

Loot drops follow a more complicated formula, based on the monster loot tables.

Some monsters (such as the "dire bear") have a fixed loot list; these monsters are not affected by luck at all.

Some monsters have no loot entry at all. In this case, the game proceeds as though their loot table read {"%":30,"max":monster.level}.

Some monsters have a "%" entry in their loot table; this is a % chance that the monster will consider dropping loot. This chance is NOT affected by luck.

For any monster that doesn't have a fixed loot list, the game rolls a 50/(100+luck/2) chance of skipping loot entirely. (This gives you a 50% chance of getting loot at 0 luck, and a 66.67% chance of getting loot at 100 luck [in practice you'll never get that high].)

If both of the above checks passed, then the game proceeds to roll the actual loot:

Monsters with a list of possible items

For example:

   {
       "scrolls":"80%",
       "spear":"20%",
       "gloves":"5%",
       "cap":"5%"
   }

In these cases, each possible item rolls (its chance)*(100+luck)/100 to decide whether you get that item. You can get more than one.

Equipment generated in this way will be given a random material at most 1 level better than the item's base level, so this method will never drop equipment better than Quicksteel (unless it's generating plate mail or wings, but no monsters currently list those in this type of droplist).

Some monsters have a material in their item list; these entries don't generate any drops, because random items of a given material aren't implemented for this loot format.

Monsters with a "max" loot level

For example:

   {
       "max":5
   }

In these cases, the game first rolls a "partial level" for the item, in the range 1~(max/2).

It then rolls a number in the range 1~(partial level) for the base item level, and another number in the range 1~(partial level) for the material level.

It then tries to give you an item with exactly that base level, and exactly that material level. If no item with that base level is possible, you get nothing. If no material of that material level is possible, then you get no material (producing a junk item).

Luck plays no role at this stage; monsters that produce "max"-type loot only benefit from luck in the "skip loot" roll.