Simon could barely keep himself together. His actions were in the moment but his mind, like Vance's, was at the center of that pit of darkness. He was petrified that if one of these strings of dark touched him again something far worse than growing horns would happen to him.
With all the fear surging through him and his oxygen levels zigzagging around from the use of his power he couldn't keep himself straight enough to charge into the center with the. He saw Shima starting to make a move to help Vance fight up to Mink and he shouted "Both of you go! I'll take the back!" and he focused on keeping the rear perimeter safe, helping to move people that had been struck and throwing fire to keep himself and others from getting struck.
It wasn't long before he looked back and didn't see Vance or Shima at all, just a wall of darkness that made you feel like nothing was there. They were all swallowed up in it, Mink, Shima, Vance, and whatever other citizens had fallen to the darkness inside the cage of it with no one to haul them out.
He couldn't think about it, he had to keep the perimeter of this area safe and hope Asher and Miss America were doing okay at the other hot spots in the city being plagued by the lengthy tendrils.