Oracle

Enchantment 

Whenever a creature with flying enters the battlefield under your control, it gains haste until end of turn.
Whenever a Dragon enters the battlefield under your control, it deals X damage to any target, where X is the number of Dragons you control.

Tournooi-info

Legal in: Vintage, Legacy, Modern, Commander

Officiele rulings

11/17/2017
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.

11/17/2017
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.

11/17/2017
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.

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