The six cards that formed the three Pokmon LEGEND pairs in Reviving Legends were two Entei & Raikou LEGEND cards, two Suicune & Entei LEGEND cards, and two Raikou & Suicune LEGEND cards
The final bit of text reads: If a legendary permanent or an artifact entering or leaving the battlefield causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time. Basically, Gandalf the White can do a lot of good stuff, and being a 4/5 isnt bad either
My use of Aether Gust is not groundbreaking, as this was common practice in Standard against a similar metagame
It is a huge mana sink, but with infinite mana or a large amount of it, you mostly guarantee a loss of life enough to kill the table after they run out of permanents
These decks are balanced to play against each other, but they can also be customized to better match your playstyle or highlight your favorite characters