Nirvana

Nirvana is a legendary magic the Oración Seis dark guild is looking for. According to Brain, it has the power to turn light to darkness and vice versa. It's later revealed that it forces people to change alignments between light and darkness when they are wavering in between.

Creators
It was created by a race of humans called the "Nirvit", people who were always neutral in wars. To try to keep peace in the world, they constructed Nirvana to force people to stop wars. However, they ultimately failed and decided to seal Nirvana and created a guild to watch over it. This guild became known as the Cait Shelter Guild. We later find out that Nirvana did actually work but took much darkness within itself, which affected the Nirvit tribe living on it. They ended up killing one another due to this till only Roubaul remained. Roubaul then stay within the world as a spirit and waited until someone strong enough was able to destroy his tribe's creation.

Stages of Nirvana
It was stated by Hibiki Laytis that in the 'Final Stage' of Nirvana, Light and Darkness would completely switch places; however, he mentions that there are intermediate stages.

First stage
In the first stage, a black pillar of light ascends from Nirvana itself, and this causes those who have doubts and who are wavering in between Light and Darkness due to powerful negative thoughts or otherwise to completely switch sides, shown when Sherry attacked Gray Fullbuster with her Wood Doll, after having seen Lyon Bastia presumably die at the hands of Racer, and also when Hoteye hugged Jura Nekis after proclaiming that only love was needed to live.

Second stage
In the next stage, activated by Brain, Nirvana erupts upwards with more towers coming out of the ground beside the former one, and a palace or castle like structure. A large mound of ground comes with it into the air, supported by long spider-like legs that appear from the surrounding area and seem to be made of flexible stone. It is yet unknown the capabilities of this stage except as a form of transportation. It appears that there doesn't have to be a person in the king's area to keep it moving. Its later revealed that the leg are each powered by a magical orb to keep the device operational and all need to be destroyed at once to stop it. Natsu and the Light Team manage to do just that, once all were destroyed. Nirvana caved in on itself and crumbled to the ground in pieces.

Known Users

 * Nirvits
 * Oracion Seis members
 * Jellal Fernandes (he activated it and then he wants to destroy it)

Trivia

 * When Nirvana first appeared, it was shown to have 8 legs, but starting from chapter 157, it only had six.
 * In the Q&A, Mirajane believes that Nirvana merely decided to take off two of its legs for no apparent reason, while Lucy thinks that those two legs became a burden to get to Cait Shelter, so it removed them to walk faster.
 * The word "Nirvana" is a special term in Indian religions, it is the state of being free from sufferings.