Sometimes when an event lasts really long (like 2 100% tanks fighting each other in prize fight) can push the timer over the 18min mark. On top of that some events leave the entire losing team death (so death timers) and if the wining team then gets the zilean buff + the nexus spawns then it's nearly impossible to win.
Welcome, to the Nexus Blitz!
Nexus Blitz is a new experimental (ALPHA!) game mode currently available on all live environments. Feel free to discuss and give feedback about it here!
(Note: This board will be removed when Nexus Blitz is removed from testing)