At first they thought the distant, malevolent screams and the burbling of groundwater unrelated. The way every terrifying sound echoed in these halls, neither was unusual. It wasn't even odd to hear both at the same time. None of them thought anything of it, until the shrieking seemed to grow louder.

"What is that?" Pranvera whispered, and picked her head up to stare up the hall the way she thought the sound must be coming. It was difficult to tell- like tracking the movement of a nervous fly. 

"Who knows..." Bunny answered. She felt little Mouse press close against her hocks. "Whatever it is, we should get out of the w--"

That was when the floor exploded. Pranvera's bat took off up the cavernway. A great wave of once-stagnant water, of moss and bones and swept away gold shot up to the ceiling and came crashing back down. Fresa was list instantly to the rage of the great wave. Bunny and Mouse were both knocked off their feet, tumbling head over hoof and carried away down the hall, and in the midst of roiling Bunny glimpsed it.

The screaming thing.

The beast was fire, though water surged to its every size. A bare white skull gaped, blazing, empty eyed, almost a Courser but not and ever shrieking. Bunny watched her hound bite at its ankles, but with no flesh to bleed the beast barely noticed. When at last Bunny could get her hooves beneath her she had only moments to scramble out of the way as the thing lunged straight for Mouse. Its jagged jaws closed about the foal's neck, and shrill, panicked whinnies chased them both as the monster charged along the water's course. Away out of sight.