Adam was in his Soul Form and his presence was completely concealed as he observed the battle taking place and witness dozens be killed and their souls be carried away by Death Wraiths.
However, the Death Wraiths he witnessed weren't as sharp or attentive as Shinka and also didn't dare to delay their duties as they quickly collected the souls and carried them off to the underworld.
As long as they completed their duty nothing else mattered and they didn't pay heed to Adam who floated around and reached the centre of the battlefield that had a large open space and was where he found the most powerful of all the cultivators.
Hundreds of Illusion Stones were currently in use and the restriction in place for entering the space of the Illusion Stone was that one must be a cultivator, and it was the middle of the night in a empty area outside the city, so it was unlikely that any people would be there.