Terror is a Death Magic spell that costs six spell points and causes a single target within the caster's line of sight to lose its two next turns. It is only available to the nightmare and dark champion, and cannot be used by heroes.
Whatever they fear - snakes, heights, spiders, or being buried alive - for a few moments they will experience this irrational terror in the worse way possible!
This is like an improved version of the Wasp Swarm or Confusion spells, taking units out of play for two turns instead of one. Nightmares are able to cast it once per combat, while dark champions can cast it three times.