The Exodus

Stories are passed down the generations among the Deep Dark tribe of their origins and the events that caused them to end up where they are now. Once, the Deep Dark was not united as it is today. Members of several families, their names now long forgotten, listened to the warnings of their elders and were forced together by the coming tragedy that would be the collapse.
It is said a handful of seers foresaw what was about to happen to the world and set about to save as many of their people as possible. They figured the only way to escape extinction was to head deep underground, far from the reach of what was to come. Not all of the Tabaxi were willing to listen, judging the warning to be political maneuvering by the seers instead, and many smaller groups and individual Tabaxi never could be warned in time.
Those willing left their homelands behind to venture into the caverns beneath [insert mountain name]. Only a handful of the eldest of the tribes remained behind; warriors, seers and diplomats. Their goal was to delay the inevitable as long as possible, to give their people as much time to reach safety.
When nuclear fire started raining down from the sky, and the world shook by its impact, most of the Tabaxi deep underground barely noticed, keeping their mind from everything but their destination and survival for the time being. The mourning of those left behind would wait until the united tribes were settled at their new home.