  Finite-${\mathbf Q}$ magnetic instabilities are rather common in frustrated
magnets. When the magnetic susceptibility is maximized at multiple-${\mathbf
Q}$ vectors related through lattice symmetry operations, exotic magnetic
orderings such as vortex and skyrmion crystals may follow. Here we show that a
periodic array of nonmagnetic impurities, which can be realized through charge
density wave ordering, leads to a rich phase diagram featuring a plethora of
chiral magnetic phases, especially when there is a simple relation between the
reciprocal vectors of the impurity superlattice and the magnetic ${\mathbf
Q}$-vectors. We also investigate the effect of changing the impurity
concentration or disturbing the impurity array with small quenched randomness.
Alternative realizations of impurity superlattices are briefly discussed.
