Scourge of Valkas
Creature — Dragon
Flying
Whenever this creature or another Dragon you control enters, it deals X damage to any target, where X is the number of Dragons you control.
: This creature gets +1/+0 until end of turn.
Lucas Graciano
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.
(wotc • 2017-11-17)
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.
(wotc • 2017-11-17)
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.
(wotc • 2017-11-17)
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.
(wotc • 2017-11-17)