Flying
Whenever Scourge of Valkas or another Dragon enters the battlefield under your control, it deals X damage to any target, where X is the number of Dragons you control.
{R}: Scourge of Valkas gets +1/+0 until end of turn.
If a Dragon entering the battlefield causes Scourge of Valkas's ability to trigger but leaves the battlefield before that ability resolves, that Dragon still deals damage.
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.