Although EGU had a magic circle that could confuse detection, and after the time mark lost its effect, it should have confused the location directly, but to garen who had already discovered its location, it was not very effective. Since he was in the river of time, it was difficult to escape garen's perception.
In the past, garen's perception ability was based on the perception of a true dragon.
Elemental vision, energy perception, smell of living things, heat, vibrations, and so on.
However, with the passage of time, the increase in his strength, and the strengthening of his connection with the river of time, garen's current perception was mainly carried out through the river of time. Most of the defensive detection methods were not effective against garen.