The fact that you hit their mana base, and the land they replace enters with a stun counter is almost like true land destruction in the short term
The reverse, of course, shows a triangle pointing down which means that its the cards face down side, though if this is the side youre currently using, itll be face up
As Purphoros enters the battlefield, your devotion to its color will determine whether any replacement effects that affect creatures entering the battlefield apply to Purphoros
Compare that format with the current one
As for card advantage, look no further than Glimpse of Nature and Beast Whisperer and other cards that make super cheap creatures cantrip
The Ur-Dragon is the quintessential dragon commander, making your dragons cost 1 less even from the command zone while allowing you to play any color of dragons in your EDH deck