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)

Advanced Search Sets Random Syntax Aerie Worshippers Amphibious Kavu Astroquarium Azorius Keyrune Balduvian Frostwaker Belion, the Parched Blue Marvel, Adam Brashear Blue Ribbon Brudiclad, Telchor Engineer Celestial Colonnade Cerulean Wisps Chronatog Totem Creeping Tar Pit Dance of the Skywise Dimir Keyrune Disciple of Kangee Dragonshift Emergent Sequence Faerie Conclave Fishing Pole Fractalize Fylamarid Genju of the Falls Grand Architect Hall of Storm Giants Hydro-Man, Fluid Felon Indigo Faerie Izzet Keyrune Jace, Cunning Castaway Jolrael, Voice of Zhalfir Kruphix, God of Horizons Lumbering Falls Mercurial Transformation Metathran Transport Neurok Transmuter Octo Opus Ojutai Monument Olag, Ludevic's Hubris Pestered Wellguard Polymorphist's Jest Restless Anchorage Restless Reef Restless Spire Restless Vinestalk Riverfall Mimic Saint Traft and Rem Karolus Scuttling Sentinel Serpentine Ambush Shorecrasher Mimic Silumgar Monument Simic Keyrune Startling Development Stonybrook Schoolmaster Stormchaser's Talent Surge Engine Thoughtlace Turn to Frog Unctus, Grand Metatect Very Cryptic Command Wandering Fumarole

The only unique mana rock is Patchwork Banner , which costs three generic mana and taps for one mana or any color
Perfect for storing business cards, credit cards, ID, or cash, it offers convenient access without the need for a bulky wallet
To make things even more confusing, there is also Historic Brawl