Talk:Mission/@comment-94.66.60.89-20150723183849/@comment-26994942-20151201014032

Because that's how they work...

Lore-wise, portals to the Void are opened with keys, but doing so consumes the key in the process, making further escapades into the Void require you to find more keys.

I hope when they get more into lore with this new update and future updates that they reveal a bit about how keys are created, and what exactly the void is, besides just an alternate dimension (ie is it a natural occurance, is it an artificial construction made by the Orokin, etc.)