...
Uno was able to reach his main target without being noticed due to the series of stealth-enhancing techniques that supported his stealth skill.
Adding that everyone was too focused on their chants and the ritual itself, he was able to walk past everyone and stood at the center of those he was targeting unnoticed.
But there were still a few people who noticed his very unnoticeable presence the moment when he had to briefly remove the 'Void Veil' so that he could take out the prison prism.
The king of the Dark Cloud Kingdom, who was on top of the platform of the altar, sensed Uno's presence but could not do anything as he had to dedicate all his focus and energy to completing the ritual.
On the other hand, those nobles with the highest hierarchy beneath the royal family, quickly responded. "Intruder!"