Competing interactions in frustrated magnets can give rise to highly degenerate ground states from which correlated liquid-like states of matter often emerge. The face centered cubic (FCC) antiferromagnet is one of the oldest and most important models that is characterized by such a ground state degeneracy. However, there a few materials that maintain the necessary cubic symmetry at low temperatures and permit the study of the spin-dynamics of this model. In this talk, I will discuss the specific example of K2IrCl6 that realizes a j=1/2 Heisenberg-Kitaev model on the FCC lattice. I will present inelastic neutron scattering measurements on this compound that show the emergence of a “nodal-line” classical spin-liquid, where the magnetism is characterized by a three-dimensional Hamiltonian but with correlations that diverge along two dimensions and are short range along the third. This nodal line spin liquid is highly susceptible to order-by-disorder and small perturbations that cause K2IrCl6 to magnetically order at low temperatures. However, I will show that even in the ordered state, a proximity to the nodal line spin liquid enhances quantum fluctuations that control the magnetic excitations and thermodynamics of K2IrCl6. In K2IrCl6, strong quantum fluctuations act counterintuitively to stabilize a magnetic order and dictate its low energy physics, despite the order being selected by small perturbations.