There were several ways Corey could have dealt with the artifact in the archway.
He could have subtly destroyed it, and he could have even done nothing, completely believing in the fact that his status as a Demi-Paragon would be too much for the artifact to process, he could have even used only Breath of Omniscience to hide his aura and make the artifact believe that there were three individuals in the carriage, or... he could have used the power of the void to even hide in space.
There were other methods Corey could have used, and with how powerful his mind was, he had close to a hundred methods.
However, a lot of these methods had their pros and cons, and could eventually lead to other annoying situations or were just annoying for Corey to use them.
At the end of the day, he decided to use his Breath of Omniscience to completely hide his presence.
Not only that, he also placed an illusion over the artifact in case anything happened to it so that nobody would see it.
