Countdown icon

Countdown icon  –
An example of a countdown icon:
(This is example is a countdown of 2. The icon, however, may contain a 1, 2, 3, 4, or X)
When your card with a countdown icon enters play (is played face up, activated, or encountered), it nullifies itself and is discarded at the end of the specified number of your turns (regardless of when it is played or activated or who encounters it). If the card enters play during your turn, it counts down at the end of that turn. For example, your card with a countdown of 3 nullifies itself at the end of your third turn.
Note: A convenient way to keep track of your countdown icons is to turn the card 90 degrees at the end of each of your turns.