Damage over Time (DoT) Stacking: Understanding the Same-Source Rule

DoT basics: notation, paired types, independent bonuses

DoT is not an afterthought of direct damage - it runs on its own rules.

• ▸'90 Bleeding damage over 3 seconds' means 90 total across 3 seconds. Ticks land every 0.1 seconds while the on-screen number shows each second's total.
• ▸Every DoT except Bleeding has a paired direct type: Burn = Fire, Frostburn = Cold, Electrocute = Lightning, Poison = Acid, Vitality Decay = Vitality, Internal Trauma = Physical. The paired resistance mitigates the DoT (Fire resistance reduces Burn).
• ▸Conversion also follows the pair (Fire-to-Acid conversion turns Burn into Poison) - unless the destination type has no DoT (e.g., Chaos), in which case the DoT stays unconverted (see the damage conversion article).
• ▸% bonuses alone are independent: Poison grows with '+n% Poison damage', not '+n% Acid damage'. Elemental % does not boost Burn/Frostburn/Electrocute either. What does apply: each DoT's own % bonus, +% All Damage, and the attribute-derived bonuses (Cunning for Bleeding and Internal Trauma, Spirit for magical DoTs like Burn, Frostburn, Electrocute, and Poison).
• ▸'+n% Increased Duration' keeps the per-second damage and lengthens the clock, so total damage rises accordingly - a key stat for DoT builds.
• ▸DoTs from gear, buffs, and passives are delivered through weapon damage, scaling down below 100% weapon damage - and DoT damage is never subject to attack damage converted to health (ADCtH).

The stacking rule: all different sources, one strongest per same source

Whether DoTs stack is decided by their source - the number applied has no cap.

• ▸Any number of DoTs can sit on one target - no overwriting, no refreshing of existing instances, no cap on count.
• ▸DoTs from different sources all tick simultaneously. This is why DoT builds hoard DoT sources across gear, skills, and devotions.
• ▸DoTs deemed the same source normally do not stack damage: only the instance with the highest final per-second damage ticks (see the next point for the exception).
• ▸The suppressed weaker instances are not removed - they wait, and when the stronger instance expires, the next one takes over.
• ▸One exception, added in v1.3.0.0: a bug where converted DoT damage from a single source failed to stack was fixed (the official patch notes cite Scourge Strike). It concerns DoTs within one source whose damage types ended up matching through conversion, and does not change the ordinary overwrite rule when you recast the same skill.
• ▸Example (summarizing the wiki's test): poison from one weapon applied via a 300% weapon-damage skill and a 200% one counts as the same source (same individual weapon), so only the 300% instance ticks until it expires and the 200% one takes over - while poisons belonging to the two skills themselves are different sources and tick together.

The same-source rules in practice

Two axes decide it: same skill, and same individual item. Here are the confusing cases.

• ▸From skills: re-casts and multi-hits of the same skill are all one source; a different skill is a different source.
• ▸A DoT added by an item skill modifier is a separate source from the base skill's own DoT. Conversely, one modifier feeding several attacks (like a WPS-wide addition) makes those all the same source.
• ▸DoTs delivered through weapon damage (from gear, buffs, passives) are identified by where they come from, not the skill that fired them - the same armor piece's Bleed is one source no matter which skill applies it.
• ▸Items count per individual: swapping between two copies of the same weapon makes two sources, and the same component slotted into both hands makes two sources because the host items differ.
• ▸An item's innate DoT and a DoT added to it by a component or augment are also separate sources.
• ▸Damage, duration, and the crit roll lock in at application - later stat changes never affect instances already applied (damage absorption is the one real-time exception).

In practice: growing DoT damage, and defending against it

• ▸1. Spamming is re-painting. Damage growth comes from stronger single instances (that DoT's % bonus, the matching attribute - Cunning for Bleeding/Internal Trauma, Spirit for magical DoTs - and crits) and duration extension.
• ▸2. Adding sources works: separate skills, separate items, and modifier-added DoTs each tick as their own source simultaneously.
• ▸3. RR for your main type helps DoTs too - lowering the paired direct type's resistance opens up the DoT as well (see the RR article).
• ▸4. Defensively, capping the matching resistances at 80% comes first (see the resistances article); 'n% reduced ... duration' then cuts the clock directly (80% player cap).
• ▸5. For your build's real per-second numbers and durations, assemble it in Grim Tools and read the tooltips.

1. Grim Dawn Japanese Wiki: Combat Mechanics — Confirms DoT notation with 0.1s ticks and 1s display, paired-type resistance/conversion behavior, independent % bonuses (Elemental % not applying), duration extension and reduction (80% player cap), weapon-damage scaling and the ADCtH exclusion, the stacking rules (unlimited across sources; strongest-only within a source with fallback), the same-source case rules, and application-time locking with the damage-absorption exception.
2. Official Grim Dawn Game Guide: Combat — Confirms the official basics of damage types and resistances (the stacking and same-source details come from the Japanese wiki's testing writeup).
3. Official Grim Dawn Game Guide: Character Basics — Confirms the official attribute-derived damage bonuses (Cunning for Pierce/Bleeding/Internal Trauma, Spirit for magical damage).
4. Official Crate Forum: Grim Dawn v1.2.1.6 + Hotfix — Official patch notes for the verified version.
5. Official Crate Forum: Grim Dawn Version v1.3.0.0 + Hotfixes — Confirms the v1.3.0.0 fix for converted DoT damage from a single source failing to stack (the notes cite Scourge Strike), which this article now documents as an exception to the same-source rule. On 2026-08-02 all 504 v1.3.0.0 entries plus every v1.3.0.4 and v1.3.0.5 entry were read, and this is the only change affecting the mechanics this article covers - the remaining DoT entries are per-skill number tuning.