The Fallen Knight Event can be started from any Barbarian Camp, which results in Fallen Knights attacking every city in your alliance.
When it is activated the Fallen Knights will attack your alliance in twenty waves. Waves 1-9 and 11-19 attack cities, waves 10 and 20 attack the Alliance Fortress. During each wave it is the goal for each player to kill at least 50% of the attacking invaders, for which points can be scored, an increasing amount for each wave. When a city kills less than 50% it burns, a city that burns twice will no longer be attacked.
For each city as an alliance you can achieve points, so it is best to keep as many cities in the game as long as possible.
As a preparation step you should make aware everyone in the alliance knows the Fallen Knight Event is coming, so that not only as many people are online as possible, but also that people who are not online, keep their troops in their city.
During the event reinforcing other cities is very important, there are three situations in which this can be useful.
Early on the stronger players can reinforce the weaker with part of their troops, so that the weaker stay longer in the game.
At the end the weaker players can reinforce the strong to keep them longer in the game.
Since during a wave not all attacks arrive at the same time, there can be minutes between it, it is sometimes possible to during one wave, both reinforce someone and defend your own city.
As already mentioned wave 10 and wave 20 are special waves, they target the alliance fortress instead of player cities. There are some other waves that are special too, I believe wave 7, 14 and 17. Those are waves were only a relatively small number of cities is targetted, but they are targetted by a larger amount of troops. If you are not attacked during those waves, it is good to reinforce other players.
Some people will use the Fallen Knight event as an opportunity to attack your hive. Because there are many cities burning and a lot of marches, the attacker might not be easily spotted.
You do not need to be unshielded to participate in this event, the Fallen Knights will attack whether you have shield or not.
You only suffer minor losses during this event.
Do not forget to repair your Wall Defenses after the event is over.
There are several prize stages, each with both a required alliance points and individual points. You only get the prizes if both are reached.
The potential prizes include food/wood items, vip points, alliance fund, gold, elixir vial, lord EXP, In addition there are leaderboard prizes.
I hope this guide explains how the Fallen Knight Event works and how you can score many points with your alliance. If you have additional tips or questions, please share in the comment section.