Mine was whilst playing as Pergamon. I grew as an important power in the Aegean Sea and the Western part of Asia Minor.
I defeated Bithynia in a revanchism-like war, I secured a long lasting alliance with Macedon who was keeping the Balkans in check, and my trade routes were reaching as far as Egypt, Rome and Carthage.
Eventually as prophecized by the Sybil of Delphi a former great power of the east, our brothers, would rise and expand Westwards. The followers of Seleukos had reached our gates.
Pontus was reduced to ashes as they marched on, and the Ptolemaic client states of Asia Minor were easy prey as they hadn't fielded a standing army.
I decided to use the Radovid tactic (Witcher 3 fans will know) and annex my neighbors, Ptolemy's client cities and Rhodos. But it was too late. The Seleucids had already sent their armies and elephants against me. Valley after valley, field after field, brother against brother.
Greek blood had been spilt, but that wasn't the end of it. The Kingdom of Bosphoros had decided to invade me in my most dire hour.
Macedon was soon overwhelmed when a joint invasion of Sparta and Dacia was slowly grinding their armies away. My friends bowed to their new masters and were forced to renounce their alliance with me.
My fate was decided, but my last Oligarch wanted to face it on the field of battle. His brother on the other hand decided to flee to Rhodos where he wanted to establish a new dynasty, who would enact revenge and take back Pergamon.
It was a dream short lived as the citizens of Rhodos rebelled and slaughtered their foreign masters. Some say that there are other surviving members of the Pergamese Royal Dynasty, but they watch helplessly as history unfolds under their eyes with old and new borders being disputed, maps getting redrawn and rulers rising and falling.
TL;DR: I ing hate elephants.