Tier IV or perhaps Tier V(?) item that deals exponential spirit damage on every hit, H, based on the hero's spirit power, S.

Deals damage according to the following function: Damage = Base Damage x (1 + (S / 5000) )^H
For example, if the base damage is 1000, and if the spirit power is 150, then the damage dealt on concurrent hits is as follows:
Hit 1: 1000 * (1 + (150/5000) )^1 = 1030
Hit 2: 1000 * (1 + (150/5000) )^2 = 1060.9
Hit 3: 1092
Hit 4: 1125
Hit 5: 1159
Hit 6: 1194
...
Here's a graph below to demonstrate how it would grow:

It can be upgraded from Mystic Vulnerability for s4800 as an alternative to Escalating Exposure, or bought for s6400 independently.
Or perhaps it can also be a Tier V item that directly upgrades from Escalating Exposure if there are plans to bring Tier V items at any point in the future.
(Can also be called Exponential Decay or Half-Life for funsies)

Deals damage according to the following function: Damage = Base Damage x (1 + (S / 5000) )^H
For example, if the base damage is 1000, and if the spirit power is 150, then the damage dealt on concurrent hits is as follows:
Hit 1: 1000 * (1 + (150/5000) )^1 = 1030
Hit 2: 1000 * (1 + (150/5000) )^2 = 1060.9
Hit 3: 1092
Hit 4: 1125
Hit 5: 1159
Hit 6: 1194
...
Here's a graph below to demonstrate how it would grow:

It can be upgraded from Mystic Vulnerability for s4800 as an alternative to Escalating Exposure, or bought for s6400 independently.
Or perhaps it can also be a Tier V item that directly upgrades from Escalating Exposure if there are plans to bring Tier V items at any point in the future.
(Can also be called Exponential Decay or Half-Life for funsies)