Warframe

The Void is a planet you can unlock by obtaining different void keys. You can buy 5 keys for 75 platinum, earn one from logging in, and/or completing missions. Keys have four ranks of difficulty and a preset mission type. there are 4 towers in the void (I believe). You can play tower 1,2,3,4 exterminate, capture, defense, and assassinate. There is a drop down chart on warframes wikia page that show eliglbe missions that might drop a key. Once you have keys you just need to play 10 void missions.

http://warframe.wikia.com/wiki/Void_Keys

As of the Silver Grove update, this achievement is obtained by completing 10 Void Fissure missions.

This is an extremely easy achievement and most likely has already popped for anyone who has been playing this game for a decent amount. But for anyone new diving into Warframe, let me explain.

The void is basically an extra world that is only available if you (or someone in your party) has a key to enter. There is a tower for each misson type, and 4 tiers of difficulty for each.

I say most people will pop this easily because these keys can be obtained in a few ways. You can just recieve some in normal missions on various worlds, but you can also purchase void key packs. However, if you are stingy like me, the easiest way is to let someone else carry you to the void. Most completed void missions give out void keys as well, so after playing this game for a bit, you should stack up a reasonable amount for yourself. Void missions are also the main way players recieve rare items, blurprints, and mods, so it should be very easy to find games for.

Do 10 of these successfully, and you're done. Enjoy!