As some of you may know, I've been working on an original card game. It's a storytelling game, i.e. as you play cards, you have to make them fit into the ongoing story. There are, however, some rules about what happens, some of which change based on the text on each card.
In this game, there is a kind of card called a Heart. Hearts are extremely useful, and can be used for a wide variety of purposes, from healing oneself or a friend, to temporarily becoming more powerful for the purposes of playing other cards.
There are various "Foe" cards in the game. (I'm going somewhere with this, really... I'd say "trust me," but actually now would be a good time to stop reading this thread.) Foes are usually somewhat monstrous or at least menacing. One thing Hearts can be used for is to convince a Foe to switch sides. Sometimes when this happens, the Foe becomes an ally. Sometimes there are other interesting effects as well.
The current edition of the game that I'm working on is set in sort of a Victorian era, with lots of gaslight atmosphere. One of the Foe cards is called "Absinthe," as in "Absinthe the Green Fairy." While we were playing today, one of my playtesters suggested that as a side effect, if you manage to convince Absinthe to switch sides, there should be a side-effect doubling the power of any Hearts played during one selected later turn. And I had to agree, because, as he was quick to point out...
(If you have any common sense, DO NOT click on the spoiler button, leave now and preserve your sanity)