Trick.
The temperature in the hallway dropped dramatically in an instant and a gust of wind blew through the enclosed space, a sign of the sudden change in air pressure.
The Valkyries were stunned. In place of the Olympians they were about to fight were three statues made of ice, each showing the last moment before the freeze enveloped them. They struggled to understand what had just happened but the Doctor's voice quickly shook them out of their stupor.
"Venti! Take them out!"
Still confused, the green haired Valkyrie teleported above the trio ready to swing her spear. Unfortunately she was a second too late as a barrier appeared in her way. She quickly coated her weapon in the barrier breaking Rune and struck with everything she got, but the invisible walls kept coming one after the other.