I think theres a good case to be made for Heritage Druid being the guilty party, but the reason I still think its Glimpse of Natures fault is how there are fifteen other mana creatures that could be a part of a busted Glimpse of Nature deck, while Glimpse of Nature and Skullclamp are basically the only two cards that have made Elves degenerate (and I guess maybe Gaeas Cradle, if were being very generous)
The opinions are my own
Some could lock your opponent into only one kind of interaction, while others are great to have in the deck but terrible to see in your hand
Regal Force is a decent card to ramp into in a deck with lots of green mana dorks
Since Silverquill, the Disputant naturally encourages a more aristocrats-y approach to tokens, sacrificing them for value, it's great to have a card like Sedgemoor Witch, that keeps spitting out tokens which themselves give you value when they die
Collectible packaging: Beautiful illustrated box becomes part of your collection display