Emissary of Wind (Red)

When this attacks, you may put a card from your hand on the bottom of your deck. If you do, this gets go again.

Rulings

From the Part the Mistveil release notes

You may choose to put a card from your hand on the bottom of your deck when the triggered effect resolves on the stack. If you do, neither player receives priority until the entire triggered effect, including this card getting go again, is completed.

Keyword notes

Go again - Go again allows multiple actions to be played in a turn when usually playing an action with use up your action point, and therefore end your turn. A card with go again gives the controller of that card or activated ability 1 action point when it resolves.

When an action with go again resolves, its controller gains 1 action point.
Multiple instances of go again on the same card or activated ability do not stack. If a card or activated ability has multiple instances of go again when it resolves its controller gains 1 action point only.
If an action with go again does not resolve, its controller does not gain 1 action point.
You cannot reveal a card with no to Belittle. The card must have a value to its power that is 3 or less. (0 is a value)