In a 2- to 3-quart pan over medium heat, stir sugar and 1/2 cup water until the sugar is dissolved, about 2 minutes.
Add raisins, jelly, vinegar, butter, lemon juice, cloves, mace, salt, and pepper; reduce heat to low and simmer, stirring often, until raisin sauce is reduced to 2 1/4 cups, about 15 minutes.