Curse

 is an active ability, which means it will only activate once the creature has a full bloodlust counter.  For a list of all Cards with this ability, click here! 

Variations
can appear as certain activation, or with a chance to activate. It will activate during the card's turn. It can target one, several or all enemies, the increased damage taken ranges between 1 and 3.

There is a variation of Curse for every Damage School, which increase all damage taken from that school, including abilities like Fireball, for this, see School-Curse.