The Watchfire is a special building released for the 2013 Easter Event. The building was able to be purchased for 50 eggs. It could also be won in the casino during the 2013 Summer Event and the 2014 Easter Event, and received as a present in the 2014 Winter Event.
It gives a stacking 4% buff to your empire's defense bonus.
The watchfire has many useful characteristics. It is great in the higher levels for players who want to get more points. In the higher stages, PvP is the best way to get points. To prevent getting defeated, a lot of people have many watchfires. Because of the possibilities of getting a watchfire, some players have over 80 watchfires, which combined with their great buildings make them practically invincible. Two fully leveled defensive great buildings (Cathedral of St. Basil and Deal Castle), have a total of 60% defensive boost. Having 50 watchfires and two fully leveled defensive great buildings give 260% defensive boost, making the attacker no match for the defender. Watchfires are inexpensive and useful making them the majority for the 2014 Easter Event. Overall, watchfires are extremely good.