He believes more in his plan, so he didn't expose Legion's position in the information he released. He wanted to give Legion a fighting chance so that he could see what else they were hiding. This is the most important thing to him. He needs more information about them, not creating enemies for Legion.
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In the meantime, the era of conquest progressed without Legion. It had a slower speed of progress than that of the simulation, though. This is because no one could destroy the divine plane of the Tyrant Realm, so invaders couldn't enter the realm any way they wanted.
The invaders had to wait for the realm to align before they gained entry into the Tyrant Realm through the dungeons.
