There are three kinds of secrets. Ronan Lynch lives with all of them. - School assignment, actually. Based on the epilogue of the Dream Thieves [ Spoilers ]

"They knew where Glendower was. They knew where his grave was place, where he was asleep. They had already freed his daughter Gwenlian and now it was time to wake the king himself. " Gansey and the others were finally able to wake Glendower. But the journey takes some unexpected turns... [ SPOILERS FOR BLUE LILY, LILY BLUE ]