Preheat the oven to 350°F (175°C). Line two 12-cupcake tins with paper liners.

Blend cake mix, water, vegetable oil, and eggs in a large bowl. Beat with a mixer on low speed for 2 minutes. Divide batter between the two prepared cupcake tins.

Bake cupcakes in the preheated oven until a toothpick inserted in the center comes out clean, approximately 18 to 22 minutes. Cool completely and frost with white frosting.

Prepare sugar glass: Combine water, corn syrup, white sugar, and cream of tartar in a large saucepan. Bring to a boil. Use a candy thermometer to boil the syrup to 300°F (150°C), stirring constantly. Once it reaches the desired temperature, pour onto a metal baking pan to cool. Break into shards once hardened.

Prepare edible blood: Mix together corn syrup and cornstarch in a bowl. Slowly stir in water, adding more if needed, until the consistency matches blood. Add red and blue food coloring, stirring thoroughly.