In days long gone, the seed of life in Penumbra was abundant and out of control. It produced dense forestland with gigantic trees growing almost faster than they could be cut. The earth itself bulged and contracted from year to year depending on how and where the trees shot their roots, and the rivers and springs running from the mountainous north shifted accordingly.
When the cataclysm struck, it was the middle of the Penumbran summer, darkness crept over the land and winter came; endless, freezing life in its prime and so it remained for thousands of years. Yet life was destined to find its way back into this world of ice.
There are two main notum veins in Penumbra that were somewhat damaged in the cataclysm but their energy output levels were never completely smothered. In huge underground caverns in the heart of Penumbra, the Unredeemed had built gigantic notum batteries to collect their energy, and they eventually reached their full load capacity and began leaking. Gradually, the escaped notum energy caused the immutable algor within to recede somewhat and forced life to be revived as if controlled by a will that transcended the laws of nature. The leaves of the trees, frozen rock-solid and glistening with frost in the everlasting gloom, broke their icy slumber and slowly began growing again.
The descendants of the Xan race that were left behind in the cataclysm had almost died out at that point. They also benefited from this overflow of notum and slowly began to prosper. Today they each control their own side of Penumbra, and guard it fiercely.
Penumbra is an extremely hostile environment for one special reason. The powerful winds blowing on the Brink have torn meta-water from the void, petrified it into ice crystals, and spread it throughout Penumbra. They saturate the atmosphere, and for the fragile human breeds now entering the Shadowlands this combination of gas and meta-water crystals is lethal as their respiratory and sensory organs can not cope with the damage caused by the radiation from the meta-water crystals. Therefore, before venturing into Penumbra, adventurers will have to prepare themselves to find a way to survive.