The Dreamlands, sometimes the Dreamworld, are a state of being touched by all those who experience dreams. Reality there is fluid and uncertain, even more so than it is in the regular Looniverses.
Dream worlds often tend to overlap different universes, with dreamers crossing over between one world and another. Sometimes someone is sucked into another universe's dreamworld (as was Steven Walsh when he became The VAXX); new dream worlds are often created by these "Crossovers". Many Dreamlands of the Omnilooniverse and other nearby worlds are administered by the Dream Court, an organization of morally ambiguous faerie-like beings which exists to sort out all this chaos.
The principalities that create or rule over dreamworlds are often referred to as Dreamkings or Dreamqueens. In many realities, a Rotanna/Lynk is likely to be one of them.
The most thorougly explored dreamworld of the Classic Looniverse is Harnegu, which served as the source of powers for Rotanna. However, it is only one of many dreamlands the Looniverse's dreamers pass through. For instance Mark Dante, a pawn of the Century Pact, created a dreamworld replica of Hell based on Dante's Inferno, where members of Dvandom Force were tormented by their own guilt.
See also the Letters Page Dimension.