One of the enemies is a blue spike ball. If you do not kill this enemy in time, spikes come out of its body. You can still kill the monster while it’s in this spiked state, but you’ll take damage, so kill it early.
Mobile Gaming eGuide - Tips, Tricks, and Strategies for Today's Hottest Mobile Games Knightmare Tower
One of the enemies is a blue spike ball. If you do not kill this enemy in time, spikes come out of its body. You can still kill the monster while it’s in this spiked state, but you’ll take damage, so kill it early.