Additionally when paired with an item that provides invincibility, it can easily clear a room with little effort. Sacrificial Dagger can be a great item if used properly as it can block enemy tears as well as deal heavy damage. When you also have soul or demon hearts as the Razor Blade will only deal red heart damage as long as you have red heart health. Starting with the Razor Blade item allows you to get into the Whore of Babylon state right away and allows you to keep it up should you accidentally pick up red hearts.