Vall'sar

"...there instead lied a symbol burnt into the now dead grass. It was of a half-eclipsed moon set inside a five-pointed star.  An ancient symbol, predating even the written word and most spoken language, it had a simple and primal meaning to those that understood it.  It was a symbol of power, of great and terrible magnitude. It was the symbol of Vall'sar ... a representation of pure darkness, pure destruction and entropy.... pure Chaos." (The symbol of Vall'sar decimates the town of Everwillow in The Darkest Knight, chapter 5)

Vall'sar
One of the legendary Symbols of Power discovered by the Ashur upon the founding of their own ancient civilisations, Vall'sar was the symbol of destructive negativity. Its utterance or depiction could bring death to a place, person or an entire civilisation.

Vall'sar is first witnessed / mentioned in the 5th Chapter of The Darkest Knight when Lord Braxhar of Dellis'sa'lei, Shadonian * used it to destroy the Elven town of Everwillow so that two members of the rebellion and the townsfolk could escape The Crimson Elite.