The vortex grenade is a rare and deadly weapon which utilizes complex warp technology to create a vortex between real space and the warp on activation. They are very difficult to produce, with only the Adeptus Mechanicus manufactures them, and are not issued to regular troops, but to important Imperial agents such as Inquisitors or Assassins.
The Vortex Grenade takes the form of a weighty sphere, approximately the size as the fist of a grown man, consisting of an outer shell which encases a delicate and temperamental warp mechanism. The designs of the device date back to the Dark Age of Technology.
When the grenade is activated, it creates a tiny rift between realspace and the warp, a rift that becomes a vortex in the very fabric of space. In appearance the vortex is a ball of glowing blackness like a small black hole. Everyone and everything encompassed by the vortex is destroyed; all matter and energy is drawn through the vortex and it is turned into the very stuff of the warp.
Vortices are doubly dangerous, as once they are created they behave in an unpredictable and uncontrollable manner. They may shrink, expand, vanish, remain for long periods of time, move or even divide. For this reason, they can be as deadly to their user as their intended targets.
Vortex grenades first appeared as a grenade type in Warhammer 40,000: Rogue Trader and remained in use through the 2nd edition of Warhammer 40,000 as a Wargear Card. They were removed as a piece of equipment during the 3rd edition of the game, but were brought back into the 4th edition in the form of an Apocalypse Expansion Strategic Asset. The 'Tactical Asset' entry in the Apocalypse Expansion describes them as: "The most potent man-portable weapon in the galaxy."