"Snowball Monster"

This noise came from under the snow, and unlike other noises that also came from under the snow, the noise felt like something smooth gliding or rolling around on a snowy surface. 

The Snowball monster was well-known for its unique habit to roll around when they moved extremely fast. 

That gliding noise under the snow must be a Snowball monster approaching their trap! 

Finley carefully distinguished the sound below the snow and felt that there should only be one Snowball monster, so he hurriedly told the other two students about this discovery. 

"I heard the noise of one Snowball Monster and the monster is approaching us! Seniors, please get ready!" 

The one who would play the biggest role in 'taming' the monster would be Delph rather than Celia because all she could do is to kill the monster.