Percy unleashed a forbidden attack on Ronan, A move that was not supposed to be used against even the most evil of foes and was a last resort for self defense.
Alexander, Luna and Augustus who understood the true nature of the attack panicked as it almost had a gaurantee to permanently damage Ronan's body , as the devil's fire was not something that was corrosive to the extreme upon contact.
Alexander wanted to react instantly to stop the attack from reaching Ronan , however the same barrier that he had asked to set up for audience safety was the barrier that prevented him to interfere and stop the move in time as Ronan was forced to defend it himself.
Grandmother Luna shrieked in horror as she closed her eyes a tear dropping down her eyelids as she feared the worst for her grandson.
Augustus shouted at the top of his lungs " PERCY HAVE YOU LOST YOUR MIND? ". As he too banged his fists against the barrier in pure anger destroying 13 of the 17 protections at once.