Board Thread:Plants vs. Zombies 2: It's About Time/@comment-24908640-20140610113339/@comment-5513687-20140616004730

The only way to collect keys is to complete the Gargantuar level. So do that then just skip the rest. And you don't even need to do it in assending order. So if you get one key, you can just wait till Dark ages if you really want...