Over a thousand years prior to the present day, the worlds of Eluneia and Danaros were completely separate from another, each with their own multiverse. Through some multi-cosmic event that is still not understood today, the two multiverses collided.
The immediate effect was a disruption of all magic across both worlds, and planar travel becoming completely unreliable. Strange natural disasters occurred all over Danaros: massive lightning storms, tornadoes, earthquakes, as well as failing harvests and unexplained livestock deaths.
The effect on Eluneia was much more disruptive. Due to an unstable portal between Eluneia and Danaros’ Elemental Plane of Water, the oceans started to rise rapidly. Thousands died as the people fled the rising water, and many more were killed in the ensuing chaos, though historians today do not agree to the exact cause if this.
Eluneia suffered massive depopulation and extinctions, and those that survived have only recently recovered the population levels they had prior to the Cataclysm.
In the centuries following the Cataclysm, interplanar travel remained impossible as the newly merged multiverse stabilized. Eventually, wizards from Eluneia and Danaros established magical contact, leading to limited interplanar trade. The invention of Wakeportals marked a turning point, enabling ship-based travel between planes and ushering in an era of large-scale interplanar commerce. This technological breakthrough connected worlds that had never before intersected, opening up new avenues for cultural exchange and economic growth in the post-Cataclysm multiverse.