OYL stands for One Year Later. Last year, DC skipped their comics ahead one year. For the most part, the comics told us stuff that had happened during that missing year, but didn't actually show it on panel.
DC also put out a series called 52. Issues came out once a week, showing certain events of that missing year in real time. (52 is now being released in trades.)
"What Keeps You Down" is referencing the stuff that happened during/after those two events.
I didn't even think about the fic being a spoiler. I really am so very sorry.