Creature â Bird
Whenever Aetherstorm Roc or another creature enters the battlefield under your control, you get (an energy counter).
Whenever Aetherstorm Roc attacks, you may pay . If you do, put a +1/+1 counter on it and tap up to one target creature defending player controls.
You canâ€™t pay more energy counters than you have.
Some triggered abilities state that you â€œmay payâ€ a certain amount of . You canâ€™t pay that amount multiple times to multiply the effect. You simply choose whether or not to pay that amount of as the ability resolves, and no player may take actions to try to stop the abilityâ€™s effect after you make your choice.
Keep careful track of how many energy counters each player has. You may do so by keeping a running count on paper, by using a die, or by any other clear and mutually agreeable method.
If an effect says you get one or more , you get that many energy counters. To pay one or more , you lose that many energy counters. Any effects that interact with counters a player gets, has, or loses can interact with energy counters.
If a triggered ability with one or more targets states that you â€œmay payâ€ some amount of , and each permanent that it targets has become an illegal target, the ability doesnâ€™t resolve. You canâ€™t pay even if you want to.
Energy counters arenâ€™t mana. They donâ€™t go away as steps, phases, and turns end, and effects that add mana â€œof any typeâ€ to your mana pool canâ€™t give you energy counters.
Energy counters are a kind of counter that a player may have. Theyâ€™re not associated with specific permanents. (Other kinds of counters that players may have include poison and experience.)
is the energy symbol. It represents one energy counter.
You donâ€™t have to target a creature with Aetherstorm Rocâ€™s last ability. If you do choose a target, and that target becomes illegal, the ability doesnâ€™t resolve and you wonâ€™t be able to pay to put a counter on Aetherstorm Roc.
Aetherstorm Rocâ€™s second triggered ability resolves before blockers are chosen. A creature tapped this way wonâ€™t be able to block.
A creature entering the battlefield at the same time as Aetherstorm Roc causes its first triggered ability to trigger.