Two vessels of water at different temperatures are connected by a partition. Remove the partition, and the temperatures begin to equalize until they match. A similar process occurs in a spacetime with two black hole horizons when quantum fields are present.
A horizon is a boundary beyond which light cannot escape. A black hole can have two horizons, and they have different temperatures: the outer one has a nonzero temperature, while the inner one is at zero. Quantum fields filling the space between the horizons behave like a gas of particles, but their energy depends on the curvature of spacetime. Near the horizon with nonzero temperature, this energy becomes infinite.
When backreaction was taken into account, the geometry changed: the dilaton field became constant, and the metric function took an exponential form. The new geometry has two horizons at infinities, and both horizons have zero temperature. Thus, quantum fields equalize the temperatures of the horizons by restructuring spacetime itself.
In two-dimensional gravity, the horizon temperature is proportional to its surface gravity, and for the horizon at r = 0 it is zero, even though the horizon exists. This resembles an extreme black hole, but here the zero temperature arises from the degeneracy of the metric function.