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, 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 never stack damage: only the instance with the highest final per-second damage ticks.
• ▸The suppressed weaker instances are not removed - they wait, and when the stronger instance expires, the next one takes over.
• ▸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.