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As the PCs look at the alien language, a they hear a high keening shriek in their head. Once they look away, it seems that the script writhes and slithers just out of the focus of their view, only to have changed subtly once they look back. Did the PC misremember the script?
Attempts to copy the script onto paper brings in a headache, and soon blood runs from the nose and eyes of the one drawing the script. Others who look at the drawings of the abhorrent letters quickly realize and point out that the person copying the script actually drew stylized English, just reversed, backwards, or mirrored. The words in English read as warnings like “murder” or “abandon hope.”
Only one truly mad or in an altered state of consciousness can make any sense of this script.