D&Dtools1

You encase the heart of the target creature in a block of ice.
The target becomes immediately exhausted and dies in 1d3+2 rounds.
The subject is entitled to a Fortitude saving throw to survive the attack.
If the target succeeds on the save, it instead takes 5d8 points of cold damage and is not exhausted.
(The target might die from damage even if it succeeds on the saving throw).
A character attempting to save the victim of a heartfreeze spell must use a healing spell or effect on the victim as well as succeed on a DC 26 caster level check, otherwise the victim will succumb to the heartfreeze and die.
A creature immune to critical hits and sneak attacks is unaffected by heartfreeze.
Material Component: A strip of dried humanoid sinew.