The Aranea Supervoid is an undefined devoided location outside the Milky Way. It is the place where Void Spiders originated.
In the third dimension, the Aranea Supervoid is slightly outside the Local Group.
The Aranea Supervoid is an enormous empty void with few occasional strings, leftovers of Void Spider cosmic webs or just hydrogen that was atomized by the Void Spiders.
There is literally no matter in the Aranea Supervoid. The Void Spiders that somehow originated here, probably by dimension travel, create matter from cosmic webs in the void.
Aranea is the Latin name for spiders.