I could definitely see this idea implemented through special FP and Shadow conditions...
Triumph [?]
Condition • Support Area
Tokens on this condition cannot be reinforced.
Each time you play a skirmish event, place a token here. While you can spot X tokens here, all
triumph text is active.
Menace [?]
Condition • Support Area
Tokens on this condition cannot be reinforced.
Each time the Free Peoples player plays a card, you may add 2 tokens here.
Shadow: Remove X tokens from here to play a
menace minion with twilight cost X from your draw deck; that minion's
menace text triggers. Remove
or discard this condition.