Nether Void is a recurring ability in the series.
XI Nether Void is a Job Ability. Learned by Dark Knights at level 78, it enhances the absorption gained from the next Dark Magic spell casted. It lasts until the next Dark Magic spell is casted or until a minute has passed, and its recast time is five minutes.
Nether comes from Old English niþera or neoþera', meaning "down, downwards, below, beneath."
Voids are vast spaces between filaments (the largest-scale structures in the Universe), which contain very few or no galaxies.