The tubes required fuel to sustain their activity, meaning Valefky needed a steady supply for the sake of her 'friends.' Fortunately, the internal fluids of the monsters that lived in the region sufficed. She herself was unsure as to how she knew they would, yet she had been slaying them for time untold. And as she did not have the fortitude to confirm the condition of the tube-enclosed creatures, she could only carry on with her routine of taking evident lives to preserve the ambiguous existence of others.