Dragon Tempest
From Tarkir: Dragonstorm Commander set
Dragon Tempest
Enchantment
Whenever a creature you control with flying enters, it gains haste until end of turn.
Whenever a Dragon you control enters, it deals X damage to any target, where X is the number of Dragons you control.
Rulings
- The amount of damage dealt by the Dragon that entered the battlefield is based on the number of Dragons you control when the ability resolves.
- If a Dragon entering the battlefield causes Dragon Tempest’s second ability to trigger but leaves the battlefield before that ability resolves, that Dragon still deals damage.
- The two abilities aren’t mutually exclusive. If a Dragon with flying (which is most of them) enters the battlefield under your control, both abilities will trigger.