Is it
... a spaceship come through hyperjump?
... a monster come from some netherworld?
... a snackfood come out of machine?

You decide what this "thing" is, and you determine the nature of this "portal".

Don't settle for something half-assed... demand at least six-tenths of an ass from yourself and craft a mighty solution to this latest puzzler come courtesy of your trusty topic technician.

You can do it. I know you can.

Open-ended: THE THING COMES THROUGH THE PORTAL