We have presented a reliable computational method with state of the art accuracy for predicting molecular crystal polymorphs validated on a large and diverse set of molecules including a blinded study. Our validations include all of the relevant molecules from the first six CCDC blind test, other molecules studied by previous computational polymorph prediction methods, and several molecules from modern drug discovery programs. Our method not only reproduces the experimentally known polymorphs, but also suggests new low energy polymorphs that have not been observed experimentally, posing potential risks to developing the currently known forms of these compounds without carefully considering these alternative low energy structures from our calculations.