The Tsucora are the most numerous type of Quori. Whilst all quori are spirits of nightmare, the tsucora feed on fear itself, and spend much of their time crafting nightmares for mortals. They have the power to invoke fear in mortals, and most tsucora have thousands of years of experience playing off of mortal doubts and fears.
Like all quori, they require a mortal host in order to exist on Eberron, due to the destruction of Crya by the Cul'sir Dominion.