Mmm I see! Reading about Deathchill aura killing allies made me think it was an offensive aura. Clearly I was misinformed about it working like Veil of Shadows. Thank you for clarifying that.
The 25% chance is applied when an affected ally unit or yourself deals appropriate damage.
So in the case of Deathchill aura, appropriate damage can be auto attack and spells?
Edit: Read this: Grim Dawn DoTs for Dummies: A Primer
“X% chance of +X% DoT damage”, however, can apply to ANY source of the given DoT damage type.
So if I understood it right, the Frostburn DoT would only have a chance to proc if the damage source is also Frostburn?