Once the 50 years are up, the end comes in the most satisfying way possible. End of Cycle is perfect the way it is. Its the best designed crisis there is. Its not something that just randomly happens. Its a direct result of the players choice. Its not something that happens to you, its something that happens because of you. The End of The Cycle is a cosmic force that when made a deal with will grant whatever empire power beyond imagination. That's until 50 years pass then the entity will come to destroy your empire and the rest of The Galaxy, leaving your Empire to likely fall. The End of The Cycle is generally considered to be the strongest Crisis that can appear in Stellaris and are of a deadly. The End of the Cycle is a event you can get through the Shroud that gives you a lot of bonuses for roughly 50-60 months, before causing all of your inhabited worlds to be destroyed and turned into inhabitable "Shrouded Worlds". If there is a planet your species can live on, the remainder of your species will move their, like a colony.