Tower of Heaven

The Tower of Heaven (楽園の塔,Rakuen no Tō, lit. Tower of Paradise) also known as the R-System is a special structure, hypothetically allowing the restoration to life of any person.

History
The towers were a series of structures that dark mages tried to make in order to revive the dark mage Zeref. A cult that worshipped Black Magic invested a large sum of money to initiate the building of the R-System. There was seven towers originally, but the Magic Council put an end to their construction, though they never found the 8th tower off the coast of the Caelum kingdom. The Mages captured many slaves in hope of using them to complete the tower, using terrible methods to keep the slaves in line.

Once, a slave named Erza Scarlet was punished (though Shô was at fault) for leading an escape attempt and she was tortured to be made an example of, even losing her right eye in the process. Another child slave, Jellal Fernandes, came to her rescue and saved her, but was captured instead. With this, Erza led a revolt to save him which was successful, but Jellal had been brainwahsed by Ultear Milkovich and kept all the slaves at the tower (with much better conditions, however) and decided to finish the tower as he sent Erza away to "freedom."

Description
The Tower of Heaven, or "Resurrection-System" as the rumors say, allows any person to restore life to any other human. Still, to complete the process requires (apart from Tower itself) an enormous amount of magic power, about 2.7 Billion Edeas, which fund it. The only thing that produces that kind of energy is Etherion, a weapon owned by the Magic Council, as not even a combined magical power of all the mages in the continent would be enough to produce such amount of magical power. Apart from magic power, however, a "Sacrifice" is needed - a person whose magic power is on the same (or it's very close to) level as the person to be revived. The body of the sacrificed person is then fused with the magical Lacrima, and then broken down and reconstructed into the body of the person that the R-System is meant to revive.

In the interest of protecting the order of the magical world, the construction of the towers had been forbidden by the Magic Council already in the ancient times.

Years later, Jellal had completed the tower and needed a great magic power and a sacrifice (he chose Erza) to revive Zeref.

After receiving the energy from Etherion, the Tower of Heaven transformed into its complete form, a giant Lacrima crystal. It was destroyed by giant explosion after Natsu Dragneel damaged it.

Places

 * Jellal's main room
 * Hallway
 * Prison
 * Various sectors

Trivia

 * In the Del Rey version, they mistranslated that it only needs 270 Million of Edeas
 * The outer and inner appearance of the tower is completely change in the anime.