40 feet

Suddenly, the vermilion globes rose as one. Spacing themselves
uniformly, the blood bubbles formed a circular canopy. Anything beneath
that ceiling was sure to be attacked and trapped by their deadly mist, but D
went right under the center of it. They were forty feet above him, a distance
that, for all D’s leaping ability and skill with a sword, would be too much of
a gap.

3 - 5