Eresh'Ka (a literally dead language)

Eresh’Ka

Eresh’Ka is the ancient secret language of the undead, created by the long-forgotten gods of the Neverborn. Knowledge of this language is gifted upon a creature in the infinite moment when it receives the Bleak Apotheosis of undeath. All undead, despite their mortal origins or heritage, know this language. Even non-sapient undead like skeletons and  zombies understand Eresh’Ka. The language has been compared to the echo an empty tomb, the shifting of charnel ashes, and the groaning of unhallowed earth. 

Ambitious mortals might learn Eresh’Ka from an undying patron or the ancient ghoul-hide tomes of Ur. Finding such a resource is not easy, but once the mortal has access to the language, they can learn it using the normal rules for learning a new language. (For D&D 5th Edition, this means taking the Linguist feat or spending time and money. The money buys exotic psychotropic compounds used to make the mind pliable enough to contemplate the tongue of the dead.)

Learning Eresh’Ka does not leave the mortal unchanged. As they study and contemplate the blasphemous language, the subtle touch of the Neverborn tortures their corpus, permanently reducing the mortal’s Constitution score 1. However, their Wisdom score also permanently increases by 1, as their mind is further opened to forbidden truths of the universe.

It should be noted that knowledge of Eresh’Ka does not give the mortal any special influence over the undead.