Aklo

The Aklo Language
Aklo is only known to be used by Naga, though some dragons, kobolds and serpentfolk claim to have mastered the difficult language as well.

Structure
Aklo is extremely complicated in its word forms and vowel-consonant patterns. The structure of ideas is rigid and highly complex, but the actual patterns themselves are archaic, with almost all other world languages having transitioned over the millennia to smoother and easier to understand patterns.

Magical Language
Spellcasters have theorized that by its structure, the only logical application of Aklo would have been for extended conjuration rituals, for which its design seems oddly optimized.

Danger
Many mammalian spellcasters who have tried to learn Aklo have gone mad. Using a language spell to translate Aklo or read its script is dangerous! (See system notes below.)

System notes
Notes for using Aklo in D&D 5th Edition

Caution to Mammals
Something about the Aklo language inflicts 3d4 psychic damage on mammalian casters or talisman users for every turn that the mammal spends trying to understand Aklo through magical means.