Item drops

Items that drop from monsters or item boxes follow certain drop rate calculations that determine which item or any item at all drops. Certain items, outside those obtained from monster or item boxes, equally follow calculations that determine the chance to obtain them. Examples include gambling items from Coren or redeeming Lucky Coins at the Lucky Roulette minigame. If chance is involved in obtaining items, the mechanism by which it will determine whether the item drops or not is commonly referred to as a "roll".

Item rolls

A roll can be synonymously viewed as rolling a dice, where you aim for a specific dice face to obtain an item. For example, if a monster drops an item with a 1/200 drop rate, it is synonymous to rolling a 200-sided dice where you will obtain the item only when 1 specific face out of 200 faces is rolled.

Monsters

Each time an enemy is defeated, the game rolls to determine whether an item will drop, and if so, what that item will be in the following order:

1. The game rolls for event drops, such as Event Egg, Halloween Cookie, or Present (Christmas)
2. The game rolls for Music disks (1/600 across all enemies)
3. The game rolls based on the enemy's Drop anything rate (DAR) to determine if the enemy has the possibility of dropping anything else
4. The game rolls to decide if the enemy will drop its specified rare item (depending on area, Section ID, and difficulty)
5. The game rolls to determine whether the drop is Meseta, a Tool, or the enemy's set drop (1/3 chance for any of these)

The chance to obtain items from enemies can be increased with drop rate boosts. DAR boosts increase the chance to obtain any item at all from monsters, which can also help with its designated rare drop. Rare drop rate (RDR) boosts only increase the chance for the designated rare drop. However, a monster can't have more than a 100% DAR. Certain monsters already have 100% (Bosses, rare enemies) or high DAR, where DAR boosts can't be utilized fully or only partially. A similar rule applies to RDR, in which the maximum RDR can only be boosted to 7/8 (87.50%). This however only applies to very few monsters (e.g. rare Rappies from VR Temple).

Item box

Some Item boxes may be set to drop specific items (e.g. some boxes in 1-1:Planet Ragol will only ever drop Monomates), or specific categories of items (e.g. some boxes in 1-3:Subterranean Den will only ever drop Tools).

For non-drop specific item boxes, each time an item box is opened, the game rolls to determine whether an item will drop, and if so, what that item will be in the following order:

1. The game rolls to decide if the box will drop its specified rare items (depending on area, Section ID, and difficulty). In many areas, item boxes have multiple rare drops assigned to them. The roll order is from top to bottom in the Drop charts
2. The game rolls to determine whether the drop is a Weapon, Frame, Barrier, Unit, Tool or Meseta (depending on area and difficulty; Yellowboze has a higher chance to obtain Meseta from item boxes).

Item box drops are not affected by any drop rate bonuses, including (but not limited to):

• Drop anything rate (DAR);
• Rare drop rate (RDR);
• Anguish common weapon rates;
• Photon Drop drop bonuses;
• Event drop rate bonuses;
• Altered weapon percentage patterns from Anguish

Calculation

The overall chance to obtain an item is best explained in an example. Assuming the Easter event takes place, Event Eggs can be obtained by killing monsters. Claws have weapons as a set drop. The calculation of receiving a Weapon box from killing a Claw in Ultimate is executed by following the roll order from above:

• Roll for Event Egg fails: 1 - 1/500 = 499/500
• Music disk roll fails: 1 - 1/600 = 599/600
• DAR roll successful: 3/10 (30%)
• RDR roll fails: 1 - 1/64 = 59/64
• Set drop roll successful: 1/3

The overall chance can now be calculated by multiplying the above rates:

499/500 * 599/600 * 3/10 * 59/64 * 1/3 = 1/10.89 (9.18%)

From this point further calculations can be executed in a similar fashion to determine more specific drop rates, e.g. what weapon will drop and with what attributes (Weapon attribute drop tables for further information).

Drop Rate of multiple rolls

The overall chance of obtaining items is not conditional by only killing 1 monster or destroying 1 box. For multiple kills or box openings, the overall chance to receive a drop must naturally increase. However, this increase is not linear. The increase is determined by following the binomial distribution formula:

chance of at least 1 drop = 1 - (1-droprate)^(number of events)

Using the above example, the overall chance of receiving at least 1 weapon box from a Claw by killing it 10 times is:

chance of at least 1 drop = 1 - (1-1/10.89)^(10) = 1/1.62 (61.83%)

Killing more enemies naturally increases the likelihood of receiving an item, but it will never be 100% guaranteed. This is contrary to popular belief, where killing a monster X times for its 1/X item drop will give you a guaranteed drop. In reality, the overall chance in this case always comes out to roughly 63% (approaching 1-1/e, where e=Euler's number). However, this is statistically defined as the average chance where at least 1 drop will occur.

Combined drop rates

Some monsters drop the same item but with different drop rates. For a drop rate A and a drop rate B the combined drop rate C is:

C = A + B - A * B

For instance, if one enemy drops an item with a drop rate of 1/2 and another with a drop rate of 1/4, the overall chance of receiving at least 1 drop from killing both monsters is:

1/2 + 1/4 - 1/2 * 1/4 = 1/1.6 (62.5%)