The One Magic

The One Magic (一なる魔法 Ichinaru Mahō), also known as The Essence of Magic, Primordial Magic or The Magic of One, is the original source of all forms of Magic which comes from the emotion of love.

Description
The One Magic, even with the ambiguity of it over time, have its believers share a common thought about it: that it is the source of all Magic Power, an omnipotent power. It was later revealed that the source One Magic is the emotional feeling of love. After Mavis Vermillion's curse of contradiction began to consume herself she was able to kill both her and Zeref Dragneel, two immortals, breaking their curses by showing a reflection of love towards the latter, even later transferring their essence to revive Makarov Dreyar.

Previous Interpretations
So far, few interpretations have been given in the series about what truly is The One Magic. Both Makarov and Hades at one point, believed that Magic simply comes in many ways, and that it does not have one concept but that Magic is universal.

However, as Hades left on a quest to find out more about The One Magic, he gained a much more negative understanding of it, at one point claiming that it was darkness itself. He thus began to relate The One Magic with Zeref, thinking that the Black Wizard would be the key to obtain it. So much did his point of view change that he, and, by extension, Grimoire Heart, thought that in a world where The One Magic were to exist, humans incapable of using Magic would be living in a place comparable to hell, if they were even capable of living at all.

Layla Heartfilia and her daughter, Lucy Heartfilia, as well as Mavis, have an entirely different perspective, claiming that The One Magic is love.

According to Mard Geer Tartaros, when The One Magic was born, it eventually developed into many different kinds of Magic, including Curses.