The only way for a transcendent to be hurt enough to die is either with Origin energy or divine power. He sensed a lot of divine power earlier from Helios but it was like an inactive volcano. It was unused. It just shadowed everything and fooled the other gods. They didn't notice anything strange and thought Helios's prowess is from divine power. He wasn't fooled. He was able to sense the divine power and determine it to be Celestial power despite it being inactive.
If that explosion had contained divine power, his barricade would have been destroyed. That doesn't mean much on its own. But it means much when his barricade can sense the faint fluctuations of origin energy after the noise of divine power has died down.
I've started a new book titled DESTINY GAMES. Please check it