What Sly does
A card with Sly plays itself for free when it is discarded from your hand before the end of your turn. You lose the card, not the effect.
The keyword came in with the Silent rework. Eight cards carry it, and all eight are Silent cards.
How the discard has to happen
The card has to leave your hand through a discard, and it has to happen during your turn. Both halves matter.
A card still sitting in hand when the turn ends is not discarded by Sly. Read the source before you count on it.
The eight Sly cards
| Card | Cost | Effect | Upgraded |
|---|---|---|---|
| Abrasive | 3 Energy | Gain 1 Dexterity.; Gain 4 Thorns. | Gain 1 Dexterity.; Gain 6 Thorns. |
| Flick-Flack | 1 Energy | Deal 6 damage to ALL enemies. | Deal 8 damage to ALL enemies. |
| Haze | 3 Energy | Apply 4 Poison to ALL enemies. | Apply 6 Poison to ALL enemies. |
| Reflex | 3 Energy | Draw 2 cards. | Draw 3 cards. |
| Ricochet | 2 Energy | Deal 3 damage to a random enemy 4 times. | Deal 3 damage to a random enemy 5 times. |
| Sneaky | 2 Energy | Whenever another player attacks an enemy, gain 1 Block. | Whenever another player attacks an enemy, gain 2 Block. |
| Tactician | 3 Energy | Gain 1 Energy. | Gain 2 Energy. |
| Untouchable | 2 Energy | Gain 6 Block. | Gain 9 Block. |
How the Synergy Works
A Sly card needs a discard outlet to do anything. On its own it is a normal card at a normal price.
Tactician is the cleanest example. It costs 3 Energy and gives 1 Energy back, so the value comes from playing it free through a discard.
Pair the cheap discards with the expensive Sly effects. Reflex and Untouchable cost 3 and 2 Energy, and both are far better at zero.
Where to go next
Silent changes covers the rest of the rework. Cards database lists every Silent card in one place.