A beautiful synergy with Diana Stanley:
Her Twilight Blade allows her to re-play events and skills from under her - however the blade explicitly states that the card cannot then go back under Diana when "playing or committing a card in this way". However, the cancellation effect of "Fool me once..." does not happen during the play action - it happens at a later stage, when a subsequent copy of that treachery is drawn, meaning you can trigger Diana's again at this point!
This means you can infinitely recur this card in the following steps:
- You resolve the effects of a treachery.
- You play "Fool me once..." to put it into your play area.
- A copy of that treachery is drawn and therefore is cancelled, triggering Diana's effect. The card is placed under Diana and she gets a card and a resource.
- Later, you resolve the effects of another treachery.
- You exhaust Twilight Blade to play "Fool me once..." from under Diana, placing it in your play area.
- Repeat from step 3!
It took me playing three whole campaigns as Diana before I noticed this synergy. You could say... fool me thrice.