- Curses are debuffs, applying negative effects to targets for a duration.
- Normally curses must be cast at a point within line of sight of the caster, but those that apply their effects within a radius can apply to targets not in line of sight but within radius, even if there is a wall or closed door in the way. This can be a useful scouting tool, since cursed targets are illuminated.
- Using Fade and Cleansing can reduce curse length: Fade must be active at the time cursed, while Cleansing can be active after cursing since it applies to remaining curse length every two seconds. 
- Drinking from a Well will cure a curse immediately, as will visiting a healer in town.
- Only one of the following can be active on a unit at one time, as indicated by the overlay displayed above it:
- When same curse is cast on a cursed target, it will normally overwrite the previous cast if the skill level is equal or greater. Exceptions are Attract, Cloak of Shadows, Confuse and Howl, which cannot overwrite themselves and must expire before they can apply to the same target again (although in the case of Cloak of Shadows, only when cast by the same player). 
- When different curse is cast on a cursed target, it will normally overwrite the previous one. Exceptions are as follows: 
- Grim Ward can only be overwritten by Confuse and Attract
- Fleeing effects have their own hierarchy; those higher on the following list cannot be overwritten by those lower:
- Grim Ward
- Hit Causes Monster to Flee
- Confuse cannot overwrite itself or be overwritten by any of the following:
- Dim Vision
- Grim Ward
- Hit Blinds Target
- Attract cannot be overwritten by anything, including itself.
- Shrines which apply a buff for a duration can also overwrite curses, and vice versa.
- When Confuse is overwritten, some units may continue to attack each other; when a fleeing effect is overwritten, units may continue to flee. This will stop when the units make their next AI check.
- When applying poison damage, Lower Resist only applies when units are poisoned, so it can be overwritten afterwards without losing effect on previously poisoned units, even those that become Immune to Poison again.
- Although otherwise only one curse can affect a unit at a time, differing radius means that multiple curses can be used at once: higher radius curse(s) can be cast first, then lower radius curse(s) can be cast for more localised effect.
Cannot be cursed
- Possessed cannot be cursed, and neither can the following units because they are static: 
- However, Battle Cry and Cloak of Shadows still apply.
- Effects altering AI only apply to normal and minion monsters, with the following exceptions:
- Cloak of Shadows will not blind these monsters but it will still apply -% Defense (although not to Putrid Defilers, since they are bosses).