Secret Actions are a new kind of Action card, keeping your opponent in the dark until it’s too
late for them to stop you. To play a Secret Action, put it into the played area (where actions and
flipped battle cards normally go) face down. Secret Actions don’t have an immediate effect, but
wait until later in the game to do their thing, often on your opponent’s turn!
Each Secret Action has two parts. First, a Reveal condition. This tells you when to reveal the
Secret Action by turning it face up. Most Reveal conditions are things your opponent does, like
attack one of your characters or play certain kinds of cards.
Second, a When Revealed effect. This tells you what the Secret Action does when it’s finally
revealed. After a Secret Action is revealed this way, it stays in the played area and will be
scrapped at the end of the turn.
One warning though: Secret Actions won’t wait around forever. If a Secret Action is played
during your turn, it will wait until the end of your opponent’s next turn. If its Reveal condition
isn’t met by then, it will be scrapped along with all the other played or flipped cards from that
turn. It’s scrapped face up, and scrapping it this way won’t cause its When Revealed effect to
happen.
Does playing a Secret Action count as playing an Action?
[Source: WotC] 
Yes. For example, if a card says you can play an Action, it can be a Secret Action.
Can I look at my Secret Action after I play it but before its Reveal condition is met?
[Source: WotC]
Yes. Your opponent can’t look at your Secret Actions until you reveal them.
Say I have Thundercracker, Mach Warrior, who has the ability “When you play an Action ->
This gets +1 [A] until end of turn. If I play a Secret Action, does that ability trigger? Does it
trigger when the Secret Action is revealed?
[Source: WotC]
It will trigger when you first play the Secret Action. The ability won’t trigger again when the
Secret Action is revealed.
Can the Secret Action be activated on your turn with the requirement is fulfilled?
[Source: WotC]
Yes.
Secret Actions say they scrap at the end of my opponent's turn. If I
Brainstorm, Secret Action,
Peace Through Tyranny, how long does the Secret Action stay out? Will it stay out for my second turn, until it is my opponent's turn, and then scrap at the end of their turn? Or do Secret Actions just scrap at the end of the following turn, so it would scrap at the end of my second turn?
[Source: WotC]
It will stay out for your second turn and scrap at the end of your opponent's turn.
Things that effect actions also effect secret actions, which are a subset of actions.
Can you opt out of flipping a Secret Action, even if it triggers? For example, if
Infiltrate is on the field and your opponent plays an orange Action, could you choose not to negate it and hold Infiltrate's negate effect for -- hypothetically -- a second action that they use through other means?
[Source: WotC]
Revealing Secret Actions is optional. A little while back, we had answered a question pertaining to this issue and said revealing Secret Actions was mandatory. After testing and reflecting on this internally, we’ve decided to reverse that decision. If additional game actions occur after the event that would have revealed the Secret Action, the player whose Secret Action it is will be considered to have elected not to reveal it. Note: This doesn’t mean you should play fast in order to try and trip your opponent up. If your opponent has played a Secret Action, you should give them a reasonable chance to reveal it.
When you play a secret action, is it considered playing a card with no icons? Because you are playing it face-down?
[Source: WotC]
Yes, it is!
When your opponent triggers a Secret Action, does it go into the Scrap Pile or does it still scrap at the end of your opponent's turn?
[Source: WotC]
It stays in the played area and scraps at the end of your opponent’s turn.
As long as another card is allowing you to play more than one action, that action can be a Secret Action.
