This device resembles a cube of force. 

When the cube is activated it encloses an area of 1" per side, and the temperature within this area is always 65 degrees F. 

The field will absorb all cold-based attacks, i.e. cone of cold, ice storm, and even white dragon's breath. 

However, if the field is subjected to more than 50 hit points of cold in any turn (10 rounds) it collapses and cannot be renewed for 1 hour. 

If it receives over 100 hit points of damage in 1 turn the cube is destroyed. 

Note: Cold below 0 degrees F. effectively inflicts 2 hit points of cold for every -10 degrees, so that the cube is at -2 at -1 to -10 degrees F., -4 at -11 to -20, etc. Thus, at -40 degrees F. the device can withstand only 42 hit points.