The Star Sea Rules had something to say about that: wasn't it because the Goddess of Spores, Luna, and you had been advancing so aggressively and developing so quickly? Not only had you grown stronger yourselves, you'd also raised the Light Alliance's overall strength.
Just look at you. One day, you create an Origin Plane and raise a batch of God Rank powerhouses. Before long, you create another Origin Plane and raise another batch of God Rank powerhouses.
Then the first-generation Abyssal Demons suffered heavy losses under the Wrynn Alliance and Star Alliance's attacks. After that, they gave up along with the collapsing Star Alliance. No force in the entire Star Sea could hold back the Light Alliance as it continued to grow stronger.
In such circumstances, if no one intervened, the Seven Deadly Sins might not be able to do anything when they awoke.
The Star Sea Rules didn't want the balance between light and darkness to be upset, so the only option was to spawn a Source of Darkness to curb the Light Alliance's growth.
But Medivh and the Goddess of Spores, Luna, could both manage and develop their forces while protecting their domain. The Three Sources of Evil hadn't achieved the results they were supposed to.
Over the years, the Light Alliance's development had never been curbed.
All one could say was that Holy Remains Sovereign Medivh and Spore Overlord Luna were absurdly overpowered. Unless they were banned, attacks against the Light Alliance would amount to little more than a slap on the wrist.
The losses caused by all sorts of incidents were far smaller than the aid the Wrynn Alliance poured into the Light Alliance.
Those two were cautious by nature. They weren't so easy to kill.
Over the years, countless beings and factions had tried