IDIOMS

Four Horsemen of the Apocalypse

(idiomatic) Harbingers of doom; several signs which combine to imply the imminence of literal or figurative destruction.

Example: 2008, Shayna M. Steinfeld, Bruce R. Steinfeld, The family lawyer's guide to bankruptcy: forms, tips, and strategies, page iii:
  Four Horsemen of the Apocalypse,... Here and now those dread specters are: Divorce, Illness, Unemployment and Overspending. These are now the harbingers of economic doom […]
2006, Ronald Brian Adler, Lawrence B. Rosenfeld, Russell F. Proctor, Interplay: the process of interpersonal communication, page 305:
  [One authority] has identified four types of communication, which he calls the "Four Horsemen of the Apocalypse," that are signs of a marriage having problems […]