The bosses are also just as susceptible to the stat break skills as anything else
For two mana you get +1/+0, for 4 mana it's +3/+0, for 6 mana it's +6/+0, and so on
Though this Gideon's 0 ability is a standard temporary indestructible creature transformation we expect from the character, its -10 can potentially be used to close out a game, providing each of your creatures with +2/+2 while tapping down each of your opponent's creatures
Blue does this all of the time with cards like Turn to Frog
Green and red also have good ways to buff creatures, so you can play something like a Giant Growth on your creature before combat then double its power again
Also, Decks built mainly from the cards in this Booster are very powerful, making it easy to reach the Summit of the game for anyone!