A wizard with Dark Magic spells can benefit from his evil powers. He can use any Dispel card as if it were a power card in order to cast or reinforce a spell. Note, it is not permitted to use a Dispel card to boost a counter card, only to cast or reinforce the sorcerer's own spells.
The Dark Magic player must wrestle with his conscience when it comes to sacrificing his Dispels. Is it better to cast a spell now or hold back and protect yourself instead? Of course, we all know players of evil sorcerers will invariably decide to blow their Dispels... that is their inevitable and fatal error. That... and cackling as their cards are dealt.