Everything had happened in an instant, so fast that many of the other mages atop the city gates couldn’t react in time to the Coral Clan mage’s transformation.
Fortunately, Alec had been keeping an eye on him and, the moment he noticed the situation spiralling out of control, gave the immediate order to eliminate the threat.
If they had allowed the transformation to complete, the mages atop the city walls would have been vulnerable to a surprise attack, though the creature would’ve eventually been taken down, but it would have had enough time to infect others, especially since most of the mages on the wall were only Tier 3.
The only exception were the other three infected human mages, who were currently too weak to fight as they focused on gathering mana now that the virus in their bodies had been temporarily restricted.