Crescendo Event

An event that causes a horde or massive zombie onslaught. The cause is often a part of the environment that The Survivors must activate in order to progress.

Panic Events by Chapter
No Mercy

In The Sewer level, Survivors must activate a noisy lift to cross a roof and enter a warehouse. Infected pour over the metal roof and across the street below, climbing eighteen-wheelers parked below and the ladder up the lift to reach them.

Later, in The Hospital, Survivors must use an elevator. Pressing the button to cause its descent summons a horde from the surrounding walls and the hall from which they just came.

Death Toll

While scouring The Drains, the Survivors reach a flood control room. They must trigger a flood gate to drop to proceed further. Doing so summons a horde from the sewers below.

When Survivors reach the safehouse at the end of The Church level, a mysterious man known only as 'churchguy' (so called from the name of his sound file) is already inside. When asked to open the door, he will instead ring the church bells, calling forth a horde.

After leaving an office building, Survivors are confronted with a forklift holding up a cement walkway in The Town. Triggering the forklift to drop its load allows them to proceed, but not before summoning a horde.

Having arrived at the Boathouse Finale, Survivors discover a radio. They are informed by the male voice heard over it that a boat is arriving to rescue them. They must survive an onslaught of infected, then make a break for the docks just outside.

Dead Air

Upon exiting an apartment complex, the Survivors encounter The Crane from which a dumpster is suspended. They must lower the dumpster to proceed to the next rooftop. The loud noise the dumpster makes during its descent attracts a horde.

Next, clearing out The Construction Site, Survivors discover a barricaded alley with several propane tanks propped in front. Ascending the metal framework of the unfinished building usually yields molotov cocktails and pipe bombs, both useful in the horde onslaught brought on when the barricade is inevitably destroyed.

In order to proceed through the baggage handling area of The Terminal, Survivors must rev up a van crashed into the wall nearby, which will barrel through a locked gate. This difficult horde event will yield infected from the offices behind, over an adjacent pile of rubble blocking another hall, and the escalators below.

Exiting from the waiting area to the Runway Finale, Survivors discover a military plane and a voice from inside communicating over a radio. The pilot informs them that the aircraft needs fuel, and instructs them to activate a fuel pump. Once filled, the plane can carry them to safety. However, the noise the pump makes attracts a large horde.

Blood Harvest

In The Tunnel, Survivors must leave a train shed through an emergency exit, which, once triggered, sets off an alarm, calling forth a horde.

During The Bridge level, Survivors encounter a freight train with a lever they must pull to remove the brake, causing it to roll backwards and knock down a bridge. Doing so allows access to the safehouse at the end of the level, but the collision summons waves of infected.

The Survivors eventually reach a derelict farm during the Farmhouse Finale. A radio on the bottom floor of the abandoned house can be used to summon military rescue. In doing so, the team also calls the infected to their doorstep. They must stave off the horde until the vehicle arrives, which they enter from an open hatch in the back.

Miscellaneous

Cars are strewn about the map in virtually every level. Most are harmless; however, some will make a distinctive beeping noise when you fire a weapon near them. They can also be distinguished by their lights flashing on and off. Avoid these cars if at all possible. Triggering their alarm summons an otherwise avoidable horde.

During The Terminal level, Survivors are advised to stay clear of metal detectors. Walking through one will trigger an alarm, which will summon a horde.

Upon occasion, the Director will spawn hordes. These cannot be avoided and occur completely at random (with some exceptions - hordes are common while traversing the sewers, for example.)