Ghosts

Real-world spirits of the dead that choose to reside corporeally in the Unisphere. Any ghost can traverse the Unisphere, just as they can with any other person's dreams- why else would one have a dream of their departed grandmother telling them they love them and that they're okay where they are? Most ghosts only have enough energy to vaguely interact with just one dream before dissipating... But some ghosts, typically those with unfinished business, gruesome deaths, disrupted or disturbed resting places, those raised up via magic or taking on a guardian role, etc., have more energy to interact with dreams and may even reside in them solely as opposed to the real world.