So I've been doing this for about 4 hours now. What you'll need for this is: 5 rift keystones A fast thumb That's all. What you do is pay for a rift and get to the end, kill the guardian and leave. Talk to Orek and once the countdown begins stand near the obelisk and once the timer hits 1 tap A or X (if you're on PlayStation) right when it start to close. You'll enter another rift for no charge. I don't know if anyone else has found this but I did it when I was trying to finish as many rifts as I could before work. Funny how those things work eh? Enjoy!