The image of Daoloth was not shapeless, but so complex that the eye could recognize no describable shape. There were hemispheres and shining metal, coupled by long plastic rods. The rods were of a flat grey colour, so that he could not make out which were nearer; [..] wherever he glanced at the construction, he saw only the spaces between them.
-- Ramsey Campbell, "The Render of the Veils"
A being so otherworldy, that must be summoned in pitch blackness, to safeguard the sanity of the summoners. It's not about horror or vileness, it is just something that exists in multiple dimensions and cannot be witnessed in only three. Consider an optical illusion like Escher's Staircase, but in a scale that encompasses all reality in front of your eyes. Mind blown!