Mercadian Masques had rebels, spellshapers, and brought back cards with alternate casting costs
Stromkirk Captain ( Dark Ascension ) The first Vampire on this list is an all-star in Innistrad cubes, Vampire-tribal Commander decks, and in Dark Ascension limited
Nature's Chosen has some tryhard combos, but its mostly useful as a creature-untapper in decks that care about that in green like Emmara, Soul of the Accord
While the Rat drop does benefit from being one of the biggest drops we've seen so far (thanks to four copies of Rat Colony, which are currently worth almost $8 each, making just the Rat Colonies worth the $40 cost of the drop), the value of the cards in the drop is high enough that even if you cut the drop in half, it would still be on par with most of the other Secret Lairs , from a value perspective
Salt-o-Meter : A gym sessions worth of sweat #19
If you could reliably cast this off of a Mountain, a Forest, and a Swamp, that would be great, but that's not an option