While Horus was the first to detect them, it did not take long for the rest of the Depravitas in the hall and around the temple to feel the aura of the hundreds of warriors of the Sacred Races entering Lovecraft City. Horus's shock was mirrored in their eyes as they could not believe what they were witnessing.
It was not the fact that the warriors of the Sacred Races could enter that shocked them. After all, while the dimensional sphere that contained Lovecraft City was essentially impervious to outside attacks, it was connected to the main plane of reality, so entering it was simple for someone with a high mastery of the Law of Space, such as the Scarlet King.
What truly astounded them was that the Scarlet King and Sacred Races would dare to invade Lovecraft City. This was the domain of the Depravita Race in Aether, a fortress full of billions of drones at their disposal, and flooded with Depravita Essence, a resource they could use to constantly regenerate.