According to the Episode 16 trailer on Legends, the Legion does re-write the history. It cleans mean Eobard knows how to use it.
I gathered it wasn't Eobard that knows how to use it though, it was Malcom via that book? If that is indeed the case though, it'll be interesting to see how that affects the other shows, and whether it affects the Legends too (being that they're in a time ship that may be protected from any changes, same with Speedsters)... I figure if the changes to Felicity are limited, that somehow the Legends will reverse the changes (or most of them) that the LoD makes?
It's a shame really, cause there's so much potential here. Rip can restore his family to life, Sara can restore Laurel to life, Sara can restore Moira & Ollie's Dad (I forget his name), and even Shado? They can restore [dead] Snart. So much potential, and yet you can guarantee there will be so much wasted potential. I'm still intrigued what Malcom wants out of all of this, and Snart.