The iron law of the Endless Void: the more microscopic the things causing a change, the harder that change is to detect.
Changes in the microscopic world were not as obvious as those in the macrocosm. And with the Abyssal Moss deliberately concealing itself, it became even harder to discover.
The microscopic world contained an endless number of particles, each with its own distinct properties.
The Abyssal Moss hid itself as an ordinary particle and never displayed any abnormal behavior. No matter what observed it, it appeared to be nothing more than a normal particle. Under these circumstances, the chances of it being discovered were almost nonexistent.
In the Player World Cluster, guided deliberately by the Abyssal Moss, the Azure Sea Civilization steered clear of worlds controlled by the Player Civilization and made contact with one "clean" world after another. Residing within the individuals of the Azure Sea Civilization, the Abyssal Moss traveled from world to world, contaminating the World Cluster of the Player World on a microscopic level.
Even if a world noticed something amiss with an individual from the Azure Sea Civilization, it would only assume this was a special power from the Sinil World, not a force originating from another World Cluster.
A silent erosion was taking place throughout the World Cluster of the Player Civilization.
Like cancer cells multiplying through fission, the Abyssal Moss proliferated faster and faster.
One normal world after another became tainted with microscopic Abyssal Moss.
Throughout this process, the Abyssal Moss continued to improve itself, growing ever more concealed and elusive.
Most importantly, the Wizards knew nothing of it, the players knew nothing of it, and even the World Cluster Consciousness of the worlds where the players lived failed to notice. In the end, no one was aware of what was happening.