The most dreadful (random) event?

[Edi]

Originally Posted by ano

Never met such one. Maybe it is nations specific?

No, it's not nation specific, but it's a rare event. Infor Vadul the Ancient Presence and his horde of manikins and mandragora wipe out something on the order of 75-90% of province pop and then attack it.

That one is the absolute worst, followed by plague events. Also a bit nation dependent, Gath has a temple cost of 800, so when they get the earthquake, that's a rather non-trivial loss. Many events are somewhat dependent on what stage of the game they happen, but the plague and manikin events are never good.