When spirits defend they were trying to increase there and power.
But they didn't know that sound produced by blast was heard by evil king. He wanted to check that spirits had been killed or they have captured their palace back. For this he said"commander send 5 evils to see wether spirits had captured there palace back or not".
Mandu said"ok sir".He ordered 5 evil for checking.
5 evils gone their and they see that spirits are making some combinations. They immediately ran to evil king but spirits seen them. spirits fired their wave of thunder and fire and killed them.