Blood Moon is the event where the occuring total lunar eclipse that takes reddish tinge when fully eclipsed, resulting the sky turning red as blood. This astronomical phenomenon buffs all units' Attack to 50% Attack outside of their territory for the duration of the event.
Rat Infestation is an event where a brief outbreak of rats ensued in your village. They will devour a % of any Food not stored in Silos. The following is the percentage of impact of this disaster to your village's food supply.
Earthquake is the seismic event in form of a sudden and violent shaking of the ground, which can be damaging to buildings in your village. Usually, up until 3 of buildings would be caught fire as result of this disasters, and requires Wood to Repair them. In order to quickly undo the damage, make sure in every tile of your village at least has one Villagers so you can quickly assigned them to fix any damaged buildings.
Blizzard is a severe snowstorm with high winds and low visibility, which would hamper all production by 50%, and doubles firewood consumption. To prevent the damage, you need to stockpiling a lot of Wood and Food to prevent starvation and freezing which would cause your villagers to become sick.
Sometimes a rift between Midgard and Helheim will open at Northgard, creating a portal from which the dead will pour into the land of the living. This phenomenon would be disastrous, especially if it happened at your village. Though you may have no power to close the portals, you still have time to prepare your Warband to combat any Draugar who emerged from the portal. Each portals can only release one Draugr, as it would immediately closed after a Draugr passed through. Up untill three portals would manifest on a random tile of your village.
A seismic event exclusive to Ragnarok map. Like earthquake, it starts from a brief tremor, but this one followed by a loud rumble from a Volcano. After periodical tremors for a few months, the Volcano would spew forth multiple Molten Rocks on random tiles, which would be a major problem if some of them landed on your village tiles. If this happens, make sure the tile where one of Molten Rocks landed has one space for building a Quarry so you can deploy Miners to mine them. If the Molten Rocks left around for 3 months, it will spawn a Rock Golem that would wreaking havoc on your village.
Some Sailors who seafaring for either trade or raiding other lands ended up dying at the sea without the chance of fight a glorious battle which allow their souls to ascend to Valhalla. As result of this, they become restless Spectral Warriors who then invade the coastline of anyone's territory, including your so they have a final chance to go for Valhalla. You only have few months to prepare before they arrived, at which you must defeat them so they can have a closure to go for the afterlife.