The Void

The Void is an umbrella map area used to designate several places in Tibia which are, in some way, another dimension. This area and its subareas are necessary since all parts of the map need to be bound to a subarea since the introduction of the Measuring Tibia Quest. A similar umbrella area is the Boss Lairs which is probably used, as the name suggests, for Bosses. 
It's likely that many quest areas are part of The Void, though it's usually impossible to tell unless there's an NPC or Bestiary Creature that spawns there. 
Some parts of the map seem to be bound to the parent area directly without a subarea. For example:
* The Otherworld, as seen in the bestiary of the creatures that inhabit it;
It has 2 known subareas:
* The Dark Void
** The Devovorga's Essence Mini World Change area is part of it, seen by the presence of Dread Guardian;
** The Otherworld vortex hub is part of this subarea, seen by the presence of a Messenger of Heaven;
* The Void Underground
** It's currently unknown where exactly this subarea is used, but it was added along with or shortly after the Winter Update 2020.