Description[]
Base Damage = base damage of given aura. Aura of Decay and Arcane Mist would be 15 damage. Blood Mist would be 10 damage.
Aura stacking is a mechanic in which an entity taking damage from an aura will check if another entity is directly below it. If there exists a entity below, then that below entity will take aura damage regardless or in addition to any aura damage they may have taken from being within an aura themselves. To give an example, this means that given 2 stacked entities both hit by an aura at the same time, the top entity will take Base Damage, and the bottom entity will take Base Damage twice.(Base Damage + Base Damage).
Aura stacking works exactly as stated above, but some extension of the explanation is needed to explain the more complicated stacking that derives from this simple mechanic. Below are some examples with explanation.
Multi-Stacking[]
There are 3 scenarios to really take into account when considering common multi-stacking. These are Chain, Funnel, and Pegasus(Mount) Stacking.
Chain Stacking[]
Chain stacking often involves placing 3 entities such as pixies directly on top of each other. What this does is deal Base Damage to the top entity and then 2 * Base Damage on every minion below.
Funnel stacking[]
Funnel stacking involves using multiple entities to stack a single entity multiple times. This can be done easily with multiple small minions on top of a large minion, but it is also possible with equal size minions, which is why it is referred to here as funnel stacking.
Provided a value numEntities equals the number of entities stacking a given entity. The entities on top will take Base Damage and the entity below will take Base damage + (Base Damage * numEntities)
Pegasus (Mount) Stacking[]
Pegasus (Mount) Stacking is the idea that a player mounted on a Pegasus also stacks the Pegasus. What this means is that the Pegasus is going to take Base Damage from the aura, Base Damage for protecting the player from the aura, and Base Damage for being stacked by the player in the case that both Pegasus and mounted player/minion are hit by the aura.
In this scenario, the Pegasus is taking Base Damage * 3
Tree Stacking[]
While aura stacking is explained above, no mention was made to the actual size or shape of the hitbox or area check below the entity. While simply placing entities on top of each-other directly touching works in a lot of cases, this is not exactly how aura stacking works. Aura stacking does not require the entities to directly touch at all, and in the case of Forest Seed, you actually need to stack with a sizeable distance.
By looking at this image, you may assume that this hitbox is near the pixie that took damage and small enough that no other minions are within it, however it is slightly more complicated that that. Multiple entities cannot be aura stacked by the same singular entity. What this means is that that pixie is within the hitbox and also in a prioritized position in relation to the other entities. Put simply, this image is not meant to be used as an accurate measure of the hitbox bounds.
Zombie Pegasus Aura Damage[]
When a Pegasus is a zombified by Aura of Decay, it will not protect the player from damage. This means that Aura of Decay will only heal the Pegasus 30 and the player will take the 15 damage itself.
The zombie Pegasus's aura will deal 15 damage per turn to a mounted player, however the player does not apply stack damage to the Pegasus in this case, so the Pegasus will still only heal 15 from the aura and lose 5 for it's zombie penalty per turn.