The only condition is that the 21 damage is dealt by the same commander
Stuff like Goblins that mostly just makes your red decks even more specific or Lava Spike that makes it difficult for them to take a controlling role in any games just wont work nearly as well in my experience as offering some flexibility in draft lanes
However, by definition, using Flash exclude iOS devices most notably the iPad from game play
To behold a Dragon, you can either choose a Dragon you controlyou know, just point at itor reveal a Dragon card from your hand
A boost of three mana, or one mana on the turn you play the Monolith, is far too dangerous to be allowed to survive
Wyll and Barbarian Class have us roll one additional die, and Night Shift either increases or decreases the result by one