Sure, it costs five mana to do which is not cost efficient, but this just means you are not doing it till it is really good to do so or you have little else
Lastly, Stadium Trainer cards are played in the middle of the arena and affect both you and your opponent
The best dredge cards are Stinkweed Imp and Golgari Grave-Troll because they dredge so many cards, and Life from the Loam for its synergies
His use will really depend on the meta, and right now it seems like Aggro and Midrange decks are in
While Ratchet Bomb isnt a Modern staple, it does see play, often in colorless decks lacking removal options, as a Karn, the Great Creator tutor target or in mono-colored decks that cant easily power up Engineered Explosives as an answer to Urza's Saga tokens
Mega Greninja ex was designed by artist Susumu Maeya, who decided to use bright, summery colors to help Mega Greninja jump off the cardboard