Okay, even the mere name of this celestial mystery sounds like something ominously foreboding, as if plucked from Star Trek: THE ERIDANUS VOID.
(You know, as in, "The Klingons have disabled the ship, Captain, and we only have an hour before we are sucked into the Eridanus Void ... forever!")
The void takes its name from the constellation in which it dwells, Eridanus ("the river"), which is between Taurus and Cetus. Like many unusual deep-space discoveries, it's not something that necessarily has been seen by eyes as much as it's been detected by special telescopes. In this case, it's actually the lack of a heat signature (sort of seen as a blue "cold spot" in this image to the right) that has signaled its existence to astronomers, who "discovered" it in 2007. From what they can tell, it's a vast region of our universe with absolutely nothing in it -- no stars, galaxies or gases, nor does it contain dark matter. It appears to be a mindbogglingly giant nothing in the middle of the universe, which apparently defies some cosmological models.
If that isn't troubling enough, there are now theories that rather than a void, this deep-space anomaly may actually be a galaxy-swallowing black hole that could be over 1 billion light years across. The good news is that it's over 6 billion light years away, so it's not anything we have to worry about ... for now. Besides, we have a super massive black hole at the center of own Milky Way galaxy to deal with first.
Another more radical theory is that it's the mark of another universe beyond our own -- sort of like a flat area if you press two balloons together. Okay, not exactly like that -- I don't fully understand multiverse theory and quantum entanglements, but that's sort of how I picture it after trying to read about it.
Of course, as with any deep-space object that's on the farthest edge of our observational limits, it's probably going to take decades of study with equipment that hasn't even been developed yet to figure out exactly what it is. (Hanny's Voorwerp, anybody?)
In the meantime, the best we can do is just continue to look deeper and deeper into the heavens -- the mysteries are just out there, waiting for us.