They didn't cast a spell or anything, as doing that once, opens a gate no one wanted to see.
On the demon side of the battle, a palpable caution had descended upon the endless hordes. No low-tier demon or high tier fifth stage demons, no matter how feral, wished to be the first to get caught in the terrifying crossfire of a Sixth-Tier Mage's attack. Their sheer power and destructive capabilities were a well-known, and deeply feared, deterrent.
However, the demons' fears of collateral damage were, for now, somewhat misplaced. The Sixth-Tier Mages, formidable as they were, were currently grappling with their own escalating crisis.