Krenko makes an insane amount of creatures over the course of a game, and having an indestructible second commander that shoots damage and is able to give firebreathing to your entire board seems like its going to shoot out a lot of damage
The set doesn't have many favorite cards, and the surveil lands stand out, but for a bit of history in terms of booster pack types, the 36-pack boxes of MKM are among the cheapest
It is a powerful effect, and earns a spot on this list thanks to the history of super strong equipment that loves to get cheated into play
Besides these physical implications, it should be considered that someone (the players or a judge) will need to control the validity of the cards - which may prove difficult with some of the above points
Power is on the left, and toughness is on the right
You get some removal and the chance to benefit from abilities of opponents creatures