Build-UpGive feedback
Toxic Bullets on BebopBuild-up is a mechanic that causes bullets to accumulate a status effect over multiple hits.
Whenever a hero fires at an enemy, items and abilities with Build-up add a percentage to a meter on that target. Once the meter reaches 100%, the associated status effect is triggered. The progress of a build-up is shown as round icons above the target. Build-up per shot is reduced by damage falloff, dropping to as low as 10% of its base value at maximum range.
Build-up is a related but distinct mechanic from Stacks. Unlike stacks, which are discrete increments that scale an ongoing effect, build-up functions as a percentage meter that triggers a single status effect upon reaching 100%.
Items
Items with Build-up apply their percentage to the target through bullet hits. The build-up meter decays if the enemy does not receive any new stacks for 2 seconds, at a rate of 20% per second. Melee attacks count as 1 shot for build-up purposes. Each item's build-up per shot varies by hero, as it is affected by the hero's weapon fire rate and clip size; the exact percentages can be found on each item's page.
| Name | Effect on Trigger |
|---|---|
 Slowing Bullets |
Movement Slow |
 Weighted Shots |
Movement Slow |
 Silencer |
Silence |
 Inhibitor |
Damage Reduction and Healing Reduction |
| Toxic Bullets |
Bleed (Spirit Damage over time) |
 Spiritual Overflow* |
Fire Rate, Spirit Power and Ability Duration |
* Spiritual Overflow is a special case: its build-up affects the shooter rather than the target. However, the build-up meter still accumulates on the target being shot, meaning it is impossible to accelerate the process by shooting multiple different targets at once. It is also the only build-up source where the progress is not shown above the target.
Heroes
Some heroes have abilities that use the Build-up mechanic, accumulating a percentage on the target until the associated effect triggers.
Infernus' 
Afterburn: triggers a Burn (damage over time) effect. Light Melee attacks count as 1 stack; Heavy Melee attacks count as 2 stacks.
Mina's 
Love Bites: triggers a Spirit damage proc. Melee attacks do not contribute to build-up.
Mirage's 
Djinn's Mark: builds up stacks by shooting the target at certain intervals, triggering a Spirit damage proc either when the timer runs out, when max stacks are reached, or when detonated by Mirage. Builds up with a single bullet per stack.
Silver's 
Slam Fire (Tier 3): deals bonus damage if all 3 shots hit the same target.
Note: 
Graves' 
Essence Theft appears visually as a Build-Up, but it's actually a stacking effect, as the effect is applied over time.
Counters
Several items and abilities can mitigate or counter build-up effects:
Plated Armor provides a chance to block bullet effects from incoming shots entirely, which includes any build-up effects.- Abilities and items that disarm the enemy or reduce their fire rate, such as
Mo & Krill's 
Sand Blast, 
Disarming Hex and 
Juggernaut. 
Dispel Magic removes any existing build-up applied to the player.- Items providing Debuff Resist reduce the lingering duration of build-up as well as the duration of already triggered effects.
Debuff Reducer and its upgrades 
Spellbreaker and 
Unstoppable
Blood Tribute- Weighted Shots
Counterspell prevents trigger effect if used when build-up crosses 100% threshold, but otherwise does not prevent build-up from stacking.- Abilities and items that makes the player immune to damage, such as
Ivy's 
Stone Form or 
Ethereal Shift, will also prevent any build-up on the player.
Notes:
Metal Skin, despite providing immunity to bullet damage, does not protect against build-up in any way; shots negated by Metal Skin still contribute their full build-up percentage.
Return Fire does not build up effects against the attacker.
