Compared to our mundane world, the Warhammer world is drenched in magic. The very rocks of the planet are soaked with sorcerous power, the trees draw their sustenance from waters steeped in magic, and the air itself is impregnated with raw sorcery. Small wonder then that the creatures which live in the Warhammer world have developed a certain natural immunity to magic - an ability to resist the influence of magic upon their minds and bodies. Were this nor the case then all life would have since mutated into abhorrent forms and the world would be overrun with slithering tentacled monstrosities.
To represent this natural ability to resist the influence of magic, we have the Dispel roll. After a player has case a spell, his opponent can immediately make one attempt to dispel it using any number of his Dispel dice. Some magic items may allow a second attempt, or a re-roll, but these are exceptions and in normal circumstances only one attempt can be made to dispel a spell. You will notice that it does not matter who or what the spell bas been cast at, it can always be dispelled.
In addition, the result can be increased further by the use of magic items. Any number of magic itetns can be combined to boost the score, but the player must declare that he is using any magic items before he makes the Dispel dice roll. It is nor permitted ro roll the dice and then decide to use a magic item retrospectively. Many of these magic items can only be used once, or a limited number of times, so it is important to be clear about whether you are using them or not before rolling the dice.
To dispel a spell, the player must score the same number or higher than the caster scored to cast the spell. For example, if the caster used four dice and got a result of 20, the dispelling player must score 20 or more on his Dispel dice to dispel the spell.