How 10's 18 25 starts abrupt current decline (5,5)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

PARADISE (answer to 18) LOST (answer to 25) is an epic poem by the 17th-century English poet John MILTON (1608–1674) (answer to 10). The poem concerns the Biblical story of the Fall of Man: the temptation of Adam and Eve by the fallen angel Satan and their expulsion from the Garden of Eden. It is often considered one of the greatest literary works in the English language