Shattering

Before the Shattering, the world held the former pieces of the land together in mystical stitches. I must find ways to salvage this form at the best of my ability... Or else no living being here will ever find a way to leave where they are.

― Sanctum Tower Library (presumably Angela)

The Shattering was a calamity that threatened the world of ATLYSS in distant history. The cause of the event, along with what exactly happened during, is (currently) unknown.

Aftermath

An 'active' teleportation circle.

All I can muster now is to keep the broken world intertwined, and to shield Sanctum from darkness. Without my magic, your soul would be imprisoned, and lost forever... stuck wherever you may be.

― Angela, Mystic Guardian

In the aftermath of the Shattering, the world has been left corrupted and 'broken'. Outside the vast oceanic 'walls' of Sanctum, the world is flooded with evil, as the dead rise from their graves, ancient golems turn traitor, and hell's sludge creeps forth. The world has been broken into numerous different 'shards'. From one shard, it is near impossible to reach another shard. The act is only made possible by Angela's teleportation magicks, manifest in Sanctum's World Portal, adventurer's Recall abilities, and small teleportation circles which she had (presumably) placed herself.

The world remains threatened, as monsters from sites such as the Sanctum Catacombs and the Crescent Grove pour forth into the world. It is through the actions of adventurers, sent out by the Guardians on quests, that staves off the ever encroaching tide of corruption.

Many of Angela's available quests (and library books) indicate that she is actively studying the corruption and the affected creatures.