Another great thread Mr Titan. You have really got your brain ticking on this.
This is a great explanation of what that picture represents.
The "Original Four" heroes used the 4 Elements to imprison the ancient evil. Perhaps the evil was imprisoned in the fifth element, = The Æther (Quintessence)
http://en.wikipedia.org/wiki/Aether_(classical_element)
Over the years, the term quintessence, has become synonymous with elixirs, medicinal alchemy, and the philosopher’s stone itself.
The philosopher’s stone could be the Element 115 meteors?
I think that the original 4 heroes were buried at "Excavation Site 64" and Maxis was trying to find the original Elemental staffs? But he had to make copies. Maybe the Templar Zombies were protecting the graves of the Original 4 heroes?
Remember that the 'Ancient Ruins' are a 'Tumulus Burial Mound'. Much like the Great Pyramids, heroes are buried within. Anyway...
Awesome song analysis mate, there is so much story involved with the Zombie songs.