I grinded (ground?) for over 18 hours total and got zero keys. Char full, postmaster full, vault full, glimmer maxed, spirit bloom and spin metal up the ass, enough special ammo Syn to get 10 Invectives. I was crunching rare engrams and buying heavy ammo syn at points. Just not happy I didn't get just one. I hope HOW is better than this, I can't take much more. BTW - to top it off, I lost two legendary engrams because my post master was so full it pushed them out of the lost items.