If I have Froslass ex with the "Evanescent" Ability as my Active Pokemon and it is KO'd due to Poison, how many prizes does my opponent take?
As long as you flip heads for Evanescent, they take one prize less no matter how it is Knocked Out.
Source: Paradox Rift FAQ; TPCi Rules Team (2023-11-02)

Relevant cards

Note: All applicable cards may not be listed below.
SV4_3
SV4_3