Huh, sounds kinda like Mickey's Star Shard, if it didn't work. 'Course, that's an object and not a portal, but it's got this habit of transporting you to random worlds when you least expect it. One minute you've got it in your hand, and the next, you're shooting through space at like a million miles an hour.

[Okay, so maybe that's an exaggeration, but still! It's intense.]