Non-axisymmetric external magnetic fields are the primary control available for fusion-grade tokamaks. The use of two beneficial magnetic perturbations is discussed: (1) an external non-axisymmetric field to enhance the stability of the tokamak to neoclassical tearing modes, which when unstable can lead to a disruption. (2) A current induced in the first wall during a plasma disruption to have a fail-safe prevention of high-energy runaway electrons, which can heavily damage a fusion-scale tokamak.