The Truth

Truth is the most commonly used name for the mysterious and ethereal being that sits before The Gate and addresses alchemists who have stepped into God's domain through the use of alchemy. It appears as a pure white, nearly formless being almost indistinguishable from the rest of the endless white expanse which surrounds the Gate but for a shadowy outline which causes Truth to reflect the shape of the person it is talking to, thereby supporting its claim to be another shade of that very person. When Edward and Alphonse Elric each appeared before the Gate, Truth took on the shape of a young boy and when Izumi Curtis appeared, Truth's shape reflected that of a young woman, and again, appeared as a vigorous man to Roy Mustang.

Truth initially introduces itself as the being some people call God, the World or the Universe, at first seeming welcoming and jovial to its guests before calling attention to their hubris and opening the Gate, which forces them inside. At this point, Truth often smiles with an eerily wide grin that similar to that of the Homunculus Gluttony. When the alchemist in question returns from his or her sojourn through the Gate, Truth informs them of the necessary toll for accessing the Universe's knowledge and collects it, usually in the form of a body part which disintegrates off the alchemist and reappears on Truth's form. In this way is Truth responsible for the taking of Edward's left leg and right arm, some of Izumi's internal organs, Jude's eyes and Alphonse's entire body. It would appear that Truth's goal is to discourage humans from treading in God's domain, as it calls Edward a fool when the young boy returns and sacrifices his arm to recover his brother's soul.

Though Truth appears in Edward's dreams, mocking him, his next true appearance is in Chapter 53, when Edward crosses to the true Gate from inside Gluttony's internal imitation. Truth appears amused that Edward has not come to retrieve anything that he lost on that day four years ago. Interestingly, Truth does not seem to appear before Edward as he discovers Alphonse's Gate and the body that sits before it, but - as the body speaks to him even while its soul is in the mortal plane - it is likely that what Edward sees and speaks to is Truth wearing Alphonse's body just as it wore Ed's limbs, especially since the body is seated in the same manner as Truth whenever it appears.

Trivia

 * The Truth appeared in an extra in volume 18 of the manga where it showed Yoki attempting human transmutation and having his hair taken as a toll.
 * In a late interview with the author, Arakawa said the Truth was somewhat a 'hollow' version of oneself (as a sort of 'internal God', or conscience), a sort of 'negative' of that alchemist, which completed itself with the tolls taken by the alchemist upon seeing the Truth.