The Void is the realm from which the Xel'Naga hail, and also wherein Amon lies trapped. What exactly the void is beyond that is never really discussed, but-
...Wait, that's StarCraft...
I tend to use Wikipedia's standard, which is the 2005 series is series 1 and the 1963 one is season 1, so Curse of the Black Spot is series 3 or season… 31 I think?
Curse of the Black Spot was in Eleven's second series, I believe? Nine had one series, then Ten had...three, I think (Rose, Martha, Donna) and the specials, then regenerated into Eleven who met Amy and stuck around for three series (two with Amy, one with Clara). I think the Black Spot episode was in his second series since Rory was present, though I may be misremembering and it was his first. Which makes it either the fifth or sixth "new" series. I can't recall how the numbering goes taking into account all the "classic" series so I would guess maybe around thirty (I think Nine's series was something like the 26th series counting from the beginning of One's).
Third episode of 6th series, precisely. Should be season 32 if I m counting right. Eleventh Doctor.
I doubt it has anything to do (except for the Black Spot reference to pirate tales) with the Void, though - without spoiling the story too much, the "curse" is not what it seems, in this episode. Though it would be an interesting development !
I've mentioned my theory on another thread, but here goes:
The Void is what existed before creation, and before the Wager. It is not emptiness, in fact, its the opposite: it is the primal chaos that contains the infinite possibility of existence. Its the realm where Gods, capital G, come from, insofar as they can be declared distinct beings from the realm. It is dangerous, but not because it is evil or hostile: its just too much for mere mortals to bear. The more you touch upon the Void, the more you are transformed by it, both in form and perspective.
Under this theory, Oblivaeon is one of the Void-born Gods. So is Jansa vi Dero, and also whoever else made the Wager, if Jansa isn't that being. Its also not coincidence that the Wager turned out the way it did, nor is it coincidence that except for Oblivaeon, all the Void-touched individuals are broadly positive influences on the Multiverse. In essence, the Void "wanted" Creation and the Multiverse to happen.
( To make an analogy, if this were Lord of the Rings, the Void-born gods are the Valar. Oblivaeon is Melkor/Morgoth. The Void is Eru. )