The aethership known as the Covenant sails through the skies between worlds, propelled by the magic of her captain and crew. They are exploring the edges of the known aetheric web, following uncharted currents in search of new horizons.
Most of the time, with a competent navigator—which they have—this is not a particularly risky endeavour in its own right. The risks of exploration are largely in the form of hostile or otherwise dangerous natives, with the occasional astral beast floating between the stars to catch unwary travellers.
Occasionally, however, even the finest navigator can fall afoul of unexpected changes in the flow of the current.
The ship lurches. There is a sickening jolt.
And a whirling vortex springs up out of nowhere to envelop them, ship, sails and all. It's far too late to turn about or make any attempt to control the ship's trajectory within the wormhole; all they can do is ride it out and try to hold the ship together.
After a second that seems to last a lifetime, the vortex spits them out.