Spread the refried beans evenly in the bottom of an 8-inch baking dish to form the base layer.
Sprinkle the shredded Mexican cheese blend over the beans and place the dish under the broiler for 2 to 3 minutes until the cheese melts.
Remove the dish from the broiler and let it cool for a few minutes, then spoon the salsa over the melted cheese in an even layer.
Spread 3/4 cup of the sour cream over the salsa to cover the surface completely.
Place the remaining 1/4 cup sour cream in a small zip-top bag, snip off one corner, and pipe thin lines across the sour cream to form a spiderweb pattern.
Arrange the sliced black olives in the center to create a spider shape, then serve with tortilla chips on the side.