A Stack is an scaling effect or buff that can be increased through specific means or actions. Stacks are most often applied through dealing damage, where one instance applies one stack. Most stacking effects are built up quickly and are only temporary, disappearing all at once after their duration runs out. Additionally, there are stacking bonuses that apply directly to heroes, making them stronger, with a few of these bonuses sometimes being permanent. Only a handful of heroes can infinitely stack, allowing them to constantly scale as a game goes on.
While most stacking items effects are temporary, 
Glass Cannon and 
Restorative Locket are the only items to semi-permanently keep their stacks, and require certain conditions to lose them.
Items with Stacking Effects
Heroes with Stacking Effects
Haze Haze's 
Fixation Fixation
- Haze gains increased damage to targets the more stacks of Fixation they have.
KelvinKelvin's 
Arctic Beam Arctic Beam
- Arctic Beam gradually applies an increasing Movement and Fire Rate Slow on enemies.
Lady Geist Lady Geist's 
Malice Malice
- Malice applies a bleed that causes targets to take increased damage from her, which can be stacked up to 5 times.
Paradox Paradox's 
Pulse Grenade Pulse Grenade
- Pulse Grenade's pulses each apply a stacking damage amp to targets, granting her increased damage against them.
Pocket Pocket's 
Barrage Barrage
- Barrage gradually increases Pocket's overall damage as it hits targets, up to 4 times per cast.
Shiv Shiv's 
Serrated Knives Serrated Knives
- Each cast applies a stack of bleed, which increases the debuff's damage over time and refreshes its duration.
Heroes with Permanent Stack Bonuses
There are currently 3 Heroes capable of infinitely stacking during a round. In theory, they can continue to scale endlessly with no diminishing returns.
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Bebop Bebop's 
Sticky Bomb Sticky Bomb
Grey Talon Grey Talon's 
Guided Owl Guided Owl
Mo & Krill Mo & Krill's 
Combo Combo