Costing six mana, and only being a 5/5 dragon with Flying and firebreathing, Shivan Dragon is nothing to write home about
However, they also read, At the beginning of each combat, until end of turn, each other creature you control gets +1/+1 if it has flying, +1/+1 if it has first strike, and so on for double strike, deathtouch, haste, hexproof, indestructible, lifelink, menace, protection, reach, trample, vigilance, and partner. So were counting all of those in this little roundup, which puts them at the top of this list
When you do, Invasion of Tarkir deals X plus 2 damage to any other target, where X is the number of cards revealed this way
Reign of the Pit Reign of the Pit perfectly encapsulates the weakness of edict effects
For instance, in an Archimandrite deck you could gain a bunch of life in your upkeep and first main phase to add a big +X/+0 buff to your commander, then use Alteration to turn it into Giggling Skitterspike