Sarkhan, Dominance Seeker

Dragons you control cost {1} less to cast.
Whenever a dragon enters the battlefield under
your control for the first time, you may deal 3
damage to any target.
{5}{p/g}{p/g}: Transform Sarkhan, Dominance Seeker.
Activate only as a sorcery. ({p/g} can be paid with
either {g} or 2 life.)