There's no cap on how much damage it takes for Thermal/Kinetic/Charged shield to gain a point of energy, which can result in it getting negative numbers. Specifically, when self:combatTalentMindDamage(t, 40, 50) is greater than 100, you can recover negative
Psi per hit.
Lines 35-37 in data/talents/psionic/absorption.lua:
local function shieldMastery(self, t)
return 100-self:combatTalentMindDamage(t, 40, 50)
Some of my tools for helping make talents:Melee Talent CreatorAnnotated Talent Code