As players run through stages, they will collect Items from Chests and other sources. As their run continues deeper and deeper, they will eventually find copies of items they've previously encountered. Picking up additional copies of an item is called "stacking" the item, and the total number of items of the same item is often called "stacks" of that item.
All items in the game (with the exception of equipment and 
one special item
Beads of Fealty
Seems to do nothing... but...) have amplified effects when stacking. The more stacks an item has, the more that effect is noticeable. For example, a single 
Paul's Goat Hoof
Paul's Goat Hoof
Increase movement speed.
Increases movement speed by 14% (+14% per stack). raises movement speed by 14%, which is good, but stacking 30 of them would result in a 420% increase, which is extremely good for both mobility and evasion.
Most items have one or two numerical variables that increase with stacking, but that variable is not always the same between items. For example, 
AtG Missile Mk. 1
AtG Missile Mk. 1
Chance to fire a missile.
10% chance to fire a missile that deals 300% (+300% per stack) TOTAL damage. and 
Tri-Tip Dagger
Tri-Tip Dagger
Gain +10% chance to bleed enemies on hit.
10% (+10% per stack) chance to bleed an enemy for 240% base damage. both have a chance to apply an effect that deal damage on a hit, but while stacking the former increases the damage of its effect, stacking the latter increases the chance of its effect occurring. The effect of stacking on each item is described in the item's page.
Note that for some items, the listed value in-game does not reflect the actual effect of the item. This is especially true for items that stack non-linearly, as explained below.
Contents
- 1 Stacking types
- 1.1 Linear Stacking
- 1.2 Hyperbolic Stacking
- 1.3 Reciprocal Stacking
- 1.4 Exponential Stacking
- 1.5 Special Stacking
- 2 Stacking limits
- 3 Trivia
Stacking types[]
While many items stack in the way you would expect (having 3 items triples the effect, for example), many others do not. However, most items stack consistently in one of 3 ways, and scale in a similar manner to items of the same category. These categories are outlined below.
Note that a few items have several scaling statistics that use different scaling methods. The 
Fuel Cell
Fuel Cell
Hold an additional equipment charge. Reduce equipment cooldown.
Hold an additional equipment charge (+1 per stack). Reduce equipment cooldown by 15% (+15% per stack)., for example, has both a linearly stacking (+1 charge per stack) and an exponentially stacking one (x0.85 equipment cooldown per stack).
Linear Stacking[]
Most items in the game stack linearly - meaning that for every added item, the bonus keeps increasing by the same base amount. For example, the 
Soldier's Syringe
Soldier's Syringe
Increase attack speed.
Increases attack speed by 15% (+15% per stack). increases attack speed by +15%. Having 2 of this item raises the bonus to +30%, and 10 of them to +150%.
The formula for an affected statistic is the linear function: 
, where a is the effect of one item and x is the number of items.
Hyperbolic Stacking[]
For many items using percentages (mostly for control items or items that reduce a statistic), using linear stacking would eventually lead to a 100% chance of triggering or 100% reduction. This would lead to wild imbalance from a design standpoint, such as becoming totally invulnerable or always stunning hit enemies. For this reason, these items use a different type of scaling called hyperbolic stacking.
The formula for an affected statistic is the reciprocal function: 
, where a is the effect of one item and x is the number of items.
Tougher Times
Tougher Times
Chance to block incoming damage.
15% (+15% per stack) chance to block incoming damage. Unaffected by luck. for example, uses a = 0.15 -- so with 10 Tougher Times, the block chance would be equal to 
, or a 60% chance. Once 223,696,201 Tougher Times are stacked, the block chance becomes 100% due to the limitations of floating point numbers. Interestingly, using this equation when x is 1, you end up with a 13.04% block chance as opposed to a 15% block chance.
An intuitive way of visualizing hyperbolic stacking is through a lottery example. Imagine that there are green and red tickets in a box. Every time the chance is tested, one ticket is drawn at random. If it is green, the effect triggers, otherwise it does not. By default, the box has 100 red tickets and no green tickets. Every time an item is acquired, some green tickets are added to the box. One Tougher Times would add 15 in this case. The more green tickets are added, the more they are likely to be picked over red tickets. However, there is always a chance that a red ticket is picked instead, no matter how small. This means that, in short, the more of something you have, the less the base adding is until it is as close to 0 as possible.
Reciprocal Stacking[]
This is similar in nature to the hyperbolic stacking and in fact mathematically they belong in the same category. The conceptual difference is that the formula in this case is 
. Because it does not calculate the complement of the reciprocal, the graph looks mirrored along the x-axis compared to the hyperbolic stacking, i.e., the effect is at its strongest with 1 stack and it decreases as more stacks are accumulated but it never reaches 0%.
Due to the fact that with two stacks the strength of the effect is halved, a lot of items' descriptions that use this stacking behavior incorrectly state that the effect is reduced by 50%. However, this is only true for going from 1 to 2 stacks, as at 3 stacks the effect is at 33.33% strength instead of the expected 25%.
If an item with this stacking behavior affects something unrelated to the item's effect, e.g., not its own cooldown duration, the formula may instead be 
just so even the first stack can have an effect.
Exponential Stacking[]
Some items in the game are very powerful because of their exponential stacking, meaning that their stacking effects compound each other. For instance, one stack of 
Shaped Glass
Shaped Glass
Double your damage... BUT halve your health.
Increase base damage by 100% (+100% per stack). Reduce maximum health by 50% (+50% per stack). doubles damage and halves health. Another stack will double the new damage and halve the new health, meaning that final damage would be quadrupled instead of tripled, and final health would be divided by 4 instead of 2.
The formula for an affected statistic is the exponential function: 
, where a is the effect of one item and x is the number of items.
The power of exponential stacking is that unlike both other types of stacking, they do not suffer from diminishing returns since their effects are compounding. For example, going from 50 to 51 stacks of Soldier's SyringeSoldier's Syringe
Increase attack speed.
Increases attack speed by 15% (+15% per stack). would raise the attack speed bonus from +750% to +765%, which is a negligible increase. Similarly, going from 50 to 51 Tougher TimesTougher Times
Chance to block incoming damage.
15% (+15% per stack) chance to block incoming damage. Unaffected by luck. would increase block chance from 88.2% to 88.4%, which leads to an increase in expected survivability of about 1.7%. By contrast, going from 50 to 51 Shaped GlassShaped Glass
Double your damage... BUT halve your health.
Increase base damage by 100% (+100% per stack). Reduce maximum health by 50% (+50% per stack). would still double an already monstrously high damage and halve a ridiculously low health.
Special Stacking[]
The 
Bandolier
Bandolier
Chance on kill to drop an ammo pack that resets all skill cooldowns.
18% (+10% per stack) chance on kill to drop an ammo pack that resets all skill cooldowns. uses its own special stacking formula close to hyperbolic stacking - the drop rate of an ammo box is equal to 
, where x is equal to the number of Bandoliers. While this looks like other hyperbolic stacking items, the nature of the 0.33 exponent means that the first couple Bandoliers will have a huge impact on drop chance, while the following ones will rise very slowly. More detailed information on the Bandolier's stacking can be found on its dedicated page.
Stacking limits[]
All items can be stacked infinitely (at least up to the signed 32-bit integer cap of 2,147,483,647), and their effects will also stack accordingly. However, some items have an effective limit after which further stacks have no effect.
Items with a chance to trigger that increases linearly will not gain any additional effects once the chance reaches 100%. For example, once 100% critical chance is reached through 10 
Lens-Maker's Glasses
Lens-Maker's Glasses
Gain 10% chance for hits to 'Critically Strike', dealing double damage.
Your attacks have a 10% (+10% per stack) chance to 'Critically Strike', dealing double damage., picking up additional stacks of this item will not grant stronger critical hits (unless you're playing as Railgunner, whose passive will convert it to crit damage), or have any other effect. Note that for some items linked to the proc coefficient (on-hit items), the effective limit differs depending on the character.
Focused Convergence
Focused Convergence
Increase the speed of Teleporter charging... BUT reduce the size of the zone.
Teleporters charge 30% (+30% per stack) faster, but the size of the Teleporter zone is 50% (-50% per stack) smaller. has a hardcoded cap of 3, after which neither of its effects increases.
Fuel CellFuel Cell
Hold an additional equipment charge. Reduce equipment cooldown.
Hold an additional equipment charge (+1 per stack). Reduce equipment cooldown by 15% (+15% per stack). is limited to 255 equipment charges.
Shaped GlassShaped Glass
Double your damage... BUT halve your health.
Increase base damage by 100% (+100% per stack). Reduce maximum health by 50% (+50% per stack). can only be stacked up to 127 copies, as the player will die upon collecting a 128th due to the limits of floating point numbers.
Trivia[]
- All items can be stacked to a maximum value of 2,147,483,647 - the 32 bit integer cap - before overflowing. Upon overflow, the item will reset back to 1, and act as if there is only 1 item in the player's inventory (a notable exception is the
Personal Shield GeneratorPersonal Shield Generator
Gain a recharging shield.
Gain a shield equal to 8% (+8% per stack) of your maximum health. Recharges outside of danger., which has a visual bug upon overflow). Due to this, the hard cap for all items is 2,147,483,647, with no items having a hard coded cap before this value, other than the three items listed in the previous category above. - Prior to the rework it received in the Anniversary update, the Rusted KeyRusted Key
Gain access to a Rusty Lockbox that contains a powerful item.
A hidden cache containing an item (80%/20%) will appear in a random location on each stage. Opening the cache consumes this item. used a formula similar to the lottery tickets analogy for its item rarity chances by using (metaphorical) White, Green and Red tickets - which grow at different rates - to determine the rarity of the dropped item. The new version always has the same yields as a large chest and does not stack, but consumes 1 key when opened.
| Risk of Rain 2 Wiki |
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| Survivors |
 Acrid AcridAcrid is a melee-range hybrid who uses powerful poisons to melt tanky enemies.Class: Melee / Ranged HP: 160 (+48 per level) Damage: 15 (+3 per level) Armor: 20 Umbra: Test Subject •  Artificer ArtificerThe Artificer is a high burst damage survivor who excels in fighting large groups and bosses alike.Class: Ranged HP: 110 (+33 per level) Damage: 12 (+2.4 per level) Armor: 0 Umbra: Herald of the House Beyond •  Bandit BanditThe Bandit is a high-skill combo character that can dish out devastating backstabs while weaving in and out of stealth.Class: Ranged HP: 110 (+33 per level) Damage: 12 (+2.4 per level) Armor: 0 Umbra: Desperate Outlaw •  Captain CaptainThe Captain is a unique survivor that can control the battlefield with utility and damage - with help from the UES Safe Travels.Class: Ranged HP: 110 (+33 per level) Damage: 12 (+2.4 per level) Armor: 0 Umbra: Tired Veteran •  Commando CommandoThe Commando is a jack-of-all-trades character that is reliable in all situations of the game.Class: Ranged HP: 110 (+33 per level) Damage: 12 (+2.4 per level) Armor: 0 Umbra: Cornered Gunslinger •  Engineer EngineerThe Engineer is a unique class that requires planning and positioning to be successful.Class: Ranged HP: 130 (+39 per level) Damage: 14 (+2.8 per level) Armor: 0 Umbra: Fortification Expert •  Heretic HereticThe Heretic is a powerful character who can only be accessed through extraordinary means.Class: Ranged HP: 440 (+132 per level) Damage: 18 (+3.6 per level) Armor: 0 Umbra: Unorthodoxy Risen •  Huntress HuntressThe Huntress is an extremely mobile but fragile survivor with a high damage output.Class: Ranged HP: 90 (+27 per level) Damage: 12 (+2.4 per level) Armor: 0 Umbra: Judge, Jury, Executioner •  Loader LoaderThe Loader is a slow but powerful bruiser that can use her grappling hook to uniquely navigate the environment.Class: Melee HP: 160 (+48 per level) Damage: 12 (+2.4 per level) Armor: 20 Umbra: Bionic Powerhouse •  Mercenary MercenaryThe Mercenary is a high skill melee survivor that uses his many dodges to weave in and out of combat.Class: Melee HP: 110 (+33 per level) Damage: 12 (+2.4 per level) Armor: 20 Umbra: Hired Blade •  MUL-T MUL-TMUL-T is an aggressive survivor who has the tools necessary for any job!Class: Melee / Ranged HP: 200 (+60 per level) Damage: 11 (+2.2 per level) Armor: 12 Umbra: Right Tool for the Wrong Job •   Survivors of the Void - DLC ContentRailgunner is part of the Survivors of the Void DLC. It is only available if the DLC is enabled when starting a run. Click for more info.  Railgunner Survivors of the Void - DLC ContentThis content is part of the Survivors of the Void DLC. It is only available if the DLC is enabled when starting a run. Click for more info.RailgunnerThe Railgunner is a long-range, single target survivor that can instantly kill any high priority target - and from any range. Class: Ranged HP: 110 (+33 per level) Damage: 12 (+2.4 per level) Armor: 0 Umbra: Forgotten Nomad •  REX REXREX is a half robot / half plant that uses HP to cast devastating skills from a distance. The plant nor the robot could survive this planet alone – but thankfully they have each other.Class: Ranged HP: 130 (+39 per level) Damage: 12 (+2.4 per level) Armor: 20 Umbra: Symbiotes • Survivors of the Void - DLC ContentVoid Fiend is part of the Survivors of the Void DLC. It is only available if the DLC is enabled when starting a run. Click for more info.  Void Fiend Survivors of the Void - DLC ContentThis content is part of the Survivors of the Void DLC. It is only available if the DLC is enabled when starting a run. Click for more info.Void FiendThe Void Fiend is a corrupted survivor that fluctuates between a controlled and corrupted form, each with different strengths and weaknesses. Managing this curse has become its fate. Class: Ranged HP: 110 (+33 per level) Damage: 12 (+2.4 per level) Armor: 0 Umbra: Corrupted Amnesiac |
| Environments |
Abandoned Aqueduct Abandoned Aqueduct (Stage 2)Origin of Tar You dream of sand beneath your feet. Massive skeletons and pools of tar are littered around, and a towering aqueduct pouring down tar dominates the area. • Abyssal Depths Abyssal Depths (Stage 4)Tectonic Relics You dream of fire. A hellfire-forged zone of blazing heat, the Abyssal Depths are believed to be a continuation and adaptation of the Magma Barracks from Risk of Rain. •Survivors of the Void - DLC ContentAphelian Sanctuary is part of the Survivors of the Void DLC. It is only available if the DLC is enabled when starting a run. Click for more info. Aphelian Sanctuary  Survivors of the Void - DLC ContentThis content is part of the Survivors of the Void DLC. It is only available if the DLC is enabled when starting a run. Click for more info.Aphelian Sanctuary (Stage 2) Cleansing Center You dream of clarity. • Commencement  Commencement (Final)Moon of Petrichor V You dream of glass and dirt. Large domain located above the shattered breach of  Distant Roost (Stage 1)Ground Zero You dream of waves, crashing on cliffsides. Spires of earth jut through the fog and unknown avian creatures circle far peaks guarding their broods. • Rallypoint Delta Rallypoint Delta (Stage 3)'Contact Light' Survivor Camp You dream of quiet snowfall. Rallypoint Delta is the remains of a makeshift camp constructed by a group of scattered crew members from the UES Contact Light, somewhere in the frigid tundra of Petrichor V. • Scorched Acres Scorched Acres (Stage 3)Wisp Installation You dream of wind, blowing through trees. Large, circular platforms make up the majority of the stage, and embers float through the air. •Survivors of the Void - DLC ContentSiphoned Forest is part of the Survivors of the Void DLC. It is only available if the DLC is enabled when starting a run. Click for more info. Siphoned Forest  Survivors of the Void - DLC ContentThis content is part of the Survivors of the Void DLC. It is only available if the DLC is enabled when starting a run. Click for more info.Siphoned Forest (Stage 1) Ground Zero You dream of fire and ice. The map is blanketed in a layer of snow, with large trees surrounded by platforms spanning multiple levels. • Siren's Call Siren's Call (Stage 4)Ship Graveyard You dream of wind. • Sky Meadow  Sky Meadow (Stage 5)Sprite Fields You dream of serenity. • Survivors of the Void - DLC ContentSulfur Pools is part of the Survivors of the Void DLC. It is only available if the DLC is enabled when starting a run. Click for more info. Sulfur Pools  Survivors of the Void - DLC ContentThis content is part of the Survivors of the Void DLC. It is only available if the DLC is enabled when starting a run. Click for more info.Sulfur Pools (Stage 3) Pungent Spring You dream of brimstone. Tiered lakes of shallow sulfur pools. Arcing bridges and underground caves connect the map together. • Sundered Grove Sundered Grove (Stage 4)Dormant Locus You dream of violent growth. Ancient flora has risen up to reclaim this once sacred refuge. Mazes of roots and overgrown fungus have twisted the landscape, leaving only ruins. • Titanic Plains Titanic Plains (Stage 1)Ground Zero You dream of rolling hills. Gigantic stone arches bracket the skyline, while the main play-field overlooks a vast fractured tectonic lowland. • Wetland Aspect Wetland Aspect (Stage 2)Rehabilitation Zone You dream of twisting roots. Full of ruined stone structures and swampy areas filled with water. |
| Hidden Realms |
A Moment, Fractured A Moment, Fractured (Hidden Realm)Hidden Realm: A Moment, Fractured Multiple floating islands in a void, with sharp blue crystals embedded in them. The Obelisk can be found on top of the last island. • A Moment, Whole  A Moment, Whole (Hidden Realm)Hidden Realm: A Moment, Whole A bleak and desolate realm. The refuge of the  Twisted Scavengers, safe from  Mithrix's MithrixKing of NothingHP: 1000 (+300 per level) Damage: 16 (+3.2 per level) Class: Melee / Ranged Speed: 15 m/s Armor: 20 vengeance and destruction. • Bazaar Between Time  Bazaar Between Time (Hidden Realm)Hidden Realm: Bazaar Between Time This stage serves as the shop in Risk of Rain 2. Players can purchase various Items with Lunar Coins or exchange items for higher-rarity ones in two crucibles. • Bulwark's Ambry  Bulwark's Ambry (Hidden Realm)Hidden Realm: Bulwark's Ambry The area consists of block-shaped platforms, with the Artifact Reliquary in the center. • Gilded Coast  Gilded Coast (Hidden Realm)Hidden Realm: Gilded Coast You dream of wealth. This area is where the player fights the boss Aurelionite, the Titanic Goldweaver. •Survivors of the Void - DLC ContentThe Planetarium is part of the Survivors of the Void DLC. It is only available if the DLC is enabled when starting a run. Click for more info. The Planetarium  Survivors of the Void - DLC ContentThis content is part of the Survivors of the Void DLC. It is only available if the DLC is enabled when starting a run. Click for more info.The Planetarium (Final) Cell V The Planetarium is an area somewhere within the Void, housing a collection of planets detained by the Void's denizens. It is inhabited primarily by the Voidling, the guard of the Planetarium or potentially the controller of the Void itself. • Void Fields  Void Fields (Hidden Realm)Cosmic Prison Hidden Realm accessible only through the Bazaar Between Time. Until the cell is stabilized, the Void Fields will constantly "suffocate" the player for a small percentage of their current health. • Survivors of the Void - DLC ContentVoid Locus is part of the Survivors of the Void DLC. It is only available if the DLC is enabled when starting a run. Click for more info. Void Locus  Survivors of the Void - DLC ContentThis content is part of the Survivors of the Void DLC. It is only available if the DLC is enabled when starting a run. Click for more info.Void Locus (Hidden Realm) Cell IIIVIIIIIILVIIIVLVILIVLLLVVVILIVLI You dream of potential. The Void Locus contains many Void Potentials and Cradles in place of chests, and is inhabited by Void monsters. |
| Expansions |
| Survivors of the Void - DLC Content This content is part of the Survivors of the Void DLC. It is only available if the DLC is enabled when starting a run. Click for more info.Survivors of the Void |
| Alternate Game Modes |
| Eclipse • Prismatic Trials • Survivors of the Void - DLC Content This content is part of the Survivors of the Void DLC. It is only available if the DLC is enabled when starting a run. Click for more info.Simulacrum |
| Mechanics |
| Armor • Damage • Directors • Enemy AI • Family Events • Gold • Health • Item Stacking • Lunar Coins • Movement Speed • Proc Coefficient • Survivors of the Void - DLC Content This content is part of the Survivors of the Void DLC. It is only available if the DLC is enabled when starting a run. Click for more info.Void Fog |
| Other |
| Developer Console • Development Team • Languages • Modding • Soundtrack • Unreleased Items • Version History |
