Curse is one of the basic status modifiers found in Castlevania. The properties of a Curse vary from game to game. There are two main effects:
In Aria of Sorrow, Dawn of Sorrow and Portrait of Ruin, being cursed simply drains the MP meter very rapidly.
In Symphony of the Night, Circle of the Moon, and Castlevania 64/Legacy of Darkness, curses will limit the offensive actions available to the player. In Symphony of the Night, when cursed the player cannot attack, but can still use sub-weapons and spells.
In Circle of the Moon, the player cannot attack or use sub-weapons or certain damage spells; and in Legacy of Darkness and Castlevania 64 a Curse (referred to in-game as "Vampire") restricts the use of weapons, sub-weapons, and all items except for "Purifying", which cures Curse.
Also, in Harmony of Dissonance, when cursed the player is reduced to a walking speed, and in addition cannot dash. Juste's coloration is also much darker for the duration of the Curse.
Also, in Lament of Innocence, Leon can not use his learned skills.