As soon as the infiltration started, one of the UR grade blesseds used his ability to create a barrier around everyone. This man who was responsible for this barrier was Mark and his ability was quite powerful if used properly.
He was not included amongst the top UR grades of the world because his ability was not really good for fighting along. But in a group, especially if that group had powerful people, his ability was broken.
So what his ability did was to create a barrier based on the total combat power of his team. As for who he could consider to be in his team, the people needed to directly tell him that they were willing to join his team and had to think positively about it. Only then Mark would be able to create a super strong barrier.
So the people who were a part of his team this time around were all super strong and all their combat powers were off the charts. So the barrier he was able to create was also extremely powerful.
