Increased Natural Aggression

Early in 216 AC, exploration was starting to reach outside of the Crystal Forest and into the plains and hills. Once this began, it was as if all the previously unknown dangers of the Realm were awoken at once.
There was no sign, at first, of what was to come, but it didn't stay that way for long.

The first sign actually came from the lake. We had grown used to the fish and the lake, while having unusual actions, was predictable. It changed from one day to the next.

— Author Unknown

The lake that bordered three sides of Sylcyne provided the first sign of what was to come. While it already had an interesting behavior, it became far more dangerous. The waters began to whip up into massive waves and storms, and the docile fish were joined by far more aggressive and dangerous ones. Not long after the first reports of large, aggressive birds and animals came from the forest.
There was very little time to begin preparing, as it seemed that these new creatures took great offense to people inhabiting the city. It was only a few hours after the reports that the first attack happened within the city.

Saying it was total chaos is an understatement. We found ourselves suddenly in danger is a matter of hours, with no time to prepare. Adventurers handled it the best, but there weren't many of them, let alone ones used to real danger. It was more accurate to call them explorers then Adventurers.

— Author Unknown

It took several days before Cait Monarch, still known by it's first name of The Seekers, was able to wrangle some semblance of safety for the heart of the city and several months before the walls were secured. Even then, the peace was tenuous.
The aftermath was tremedous. The once safe Forest now had to be remapped, not for changed geography but to discover the new dangers. Any expeditions outside of the Forest were put on hiatus until the mapping was finished. The Lake not only possessed new wildlife, if not as abundent, but also a changed behavior. Storms became the norm, and not just normal ones, but also ones with more esoteric effects.