FIRST OFF, I AM AWARE THAT THERE IS AN EVENT FOR EVERY MONTH. I JUST WANT TO PUT THIS IDEA OUT THERE.

So I think an awesome idea for an event would be some form of 'Nuclear Waste Spillage'
A shipment of nuclear waste goes wrong when a tanker crashes, containing the waste barrels. Nuclear waste slowly starts to spread throughout certain parts of the map, causing all sorts of freaky things to happen, like mutated enemies/mobs, with mutations like deformed limbs or extra limbs.

Toxic waste spillage also pollutes water, and can infect the prey that the lions eat
Certain prey or items may increase mutation chance of cubs, but only lethal mutation
Perhaps it can also introduce /new/ lethal mutations, some of which might not be able to be cured, perhaps the cubs can only be frozen to preserve them. (Which, I guess, could cause problems, but at the same time it can be coded in a way that these mutations also affects marks and stuff, so you don't lose anything rare)

And there could be gear left behind by humans attempting to clean the spillages which could serve as décor, such as certain elements of HAZMAT gear
Or maybe there can be barrels of the toxic waste that could also serve as décor
Also things such as mutated creatures could also be décor, say, for example, you have two-headed hyena cubs/pups (whichever is the proper terminology) or certain species of birds whose plumage colours have been affected through mutation. (Much like the Chernobyl incident, a certain type of bird developed a minor mutation wherein the breast feathers had different colouration, but died out due to those particular birds being unable to find mates.)
Of course there is also so much more potential for this, but some elements could also have downsides.
Let me know what you guys think!