It seems like there is an assload of mythogy, story, even characters in Destiny - it's just all walled off in those stupid online-only grimoire cards. It's the weirdest thing in the world. I can't fathom why they decided to hide all of it like that.
It's baffling it's not in the game. Having to look up the lore and rewards on my phone instead of the game is crazy, tons of people are never going to see that stuff.