Jars Forest Corruption

NOTE: PCs should not read this article. 
The ‘evil’ that is spreading in the Jars forest is a corruption that is the result of a mage’s backfire. The mage was attempting a complex spell involving opening a gate to the Shadow realm and instead the Gate opened to the realm of the Fey where Canus reigns supreme. The Gate is extremely unstable and opens randomly and at random locations throughout the forest and for only a short time. As it opens it blights and corrupts the surrounding forest. The gate beckons the Fey realm’s Were folk to cross over, being the servants of Canus. Once they reach the gate they immediately cross over and enter the Jar Forest. The gate is not limited to Were beings and others of the Fey realm will cross over as well including all kinds of magical beasts.
The Gateway opens in the Jars forest in a pseudo random period aligned with each new moon appearing within 1D10-5 days of the new moon. The gate will remain in the Jars forest for 6D10 min. The location of the gate can occur anywhere within the forest and to find the exact location would require a well timed Divination and a means of fast transportation (Teleport). The next gate opening will occur 1D10 New Moons afterwards.
Both the Jars Forest Tylwyth Teg and the Druids have been trying to discern this information for 100s of years. At this point they know that something is causing the corruption and that it is powerful evil/magic. They have not linked the gates to appearances of Werefolk or their link to the Fey realm and Canus. Connections with the Eldanbarig are tenuous and random. Should the leader of the brigands be questioned they will either be the most recent person to have come through the gate or possibly conducted that person onwards within the network of Canus or not (either into Militas or somewhere else within the Urtind kingdom).
The GM can scale this to his campaign but it is recommended this be a substantial effort and meant for very high level characters and will require politics (meeting with Druids and even the Jars forest Tylwyth Teg) to find all of the clues. Ultimately the gate would need to be permanently closed/controlled and this would require a very high level magician and a complex spell (requiring extensive research and preparation). Or the GM can use the Gar Marches Campaign published by Brittannia Games which chronicles the adventures of PCs as they solve the mystery of the Jars Forest Corruption.