Syr Konrad, The Grimm is labeled as an invalid card in the Colossal Tussle event when the set he comes from is a legal set for the event.
Humans are not allowed in Colossal Tussle decks
It’s in the ‘i’ portion of the event where the special supports are other rules are detailed
See “Special Rules”
ah, thank you. I had missed that. forehead slap