When the children of our people came of age, they earn the privilege of wearing the vallaslin, the blood writing. It sets us apart from the shemlen, and from the elves who have thrown their lot in with them. It reminds us that we will never again surrender our traditions and beliefs. —From Codex entry: Vallaslin: Blood Writing
Blood writing, or vallaslin in the elven language, is what the Dalish call the intricate facial tattoos worn by all adult clan members. The ink used to do so is considered sacred. Many young Dalish receive their vallaslin when they are around 18 years of age, or so. When a Dalish elf comes of age, they prepare to gain the vallaslin by meditating on the gods and the ways of the Dalish, and by purifying the body and the skin. When the time comes, the Keeper of the clan applies the blood writing. This is done in complete silence. Cries of pain are taken as signs of weakness. If a young elf cannot tolerate the pain of the blood writing, they are deemed unready to undertake the responsibilities of an adult. The keeper may stop the ritual if they decide that the one gaining the vallaslin is not ready. Blood writing is at least in part a religious practice, and there are different designs of blood writing representing deities in the Elven Pantheon.
“Whatever we were before, we are now the Inquisition.” — The Inquisitor This article contains spoilers for Dragon Age: Inquisition. Click here to reveal them.
According to Solas, the use of vallaslin during the time of Elvhenan is a much more controversial concept than believed by modern elves -- the Dalish in particular. He reveals that, in the days of Arlathan, the tattoos were not signs of patronage to the various elven gods but, in fact, slave markings--signs of ownership--when noble elves enslaved the lower classes; they were representations of the gods that the nobles favored. Abelas and the Sentinels of the Temple of Mythal have vallaslin dedicated to Mythal, etched on their faces.
A text on the carved tablet found in the Temple of Mythal tells of "the eventual failing" of elven markings, that lead to "the inevitable and troubling freedom".