Frostbite and Hypothermia
Basic rules for surviving cold weather can be found in the fifth edition rules. Characters who aren’t prepared for cold weather or who are exposed to extreme, unnatural, or magical cold can experience both hypothermia and Frostbite. Under those Conditions, Characters must make Constitution Saving Throws to avoid harm; the GM determines when Saving Throws are called for and the DC for each one. Each failed saving throw increases the risk and damage, as described below.
Stage 1: Frostnipped. The skin itches, aches, and becomes numb. Yellow and white patches form. Frostnipped Characters have a –2 penalty on Strength and Dexterity checks.
Stage 2: Shiverstruck. The character gains one level of Exhaustion, shivers uncontrollably, and his or her teeth chatter. A shiverstruck Spellcaster must make a successful DC 10 Constitution check (with disadvantage because of exhaustion) to Cast a Spell with a verbal or somatic component; if the check fails, the spell slot isn’t expended. Tasks such as getting into or out of armor take twice as long.
Stage 3: Kissed by the Ice Maiden (Hypothermia). The character gains a level of Exhaustion and can’t recover from Exhaustion until after a Long Rest in a warm Environment. The character’s skin develops black blisters but the character’s body is numb—which may initially seem a relief. A hypothermic character is only superficially aware of his or her surroundings and may trudge past shelter or blunder into Monsters or Hazards without realizing it.
Even simple activities such as drawing or sheathing a weapon, Loading a crossbow, or retrieving something from a pouch or pack require a successful DC 10 Dexterity check (made with disadvantage from exhaustion) to accomplish without fumbling and dropping the item. This can be avoided if the character takes four times longer than normal to do simple things. More complex tasks, such as starting a fire with flint and steel, are impossible.
Stage 4: Frostbitten. The character gains a level of Exhaustion and becomes Incapacitated. Eventually organs fail, flesh dies and becomes gangrenous, teeth freeze and Shatter, fingers and toes snap off, and other permanent Injuries occur. The Effect of such losses is determined by the GM. Every additional failed Constitution saving throw at this level of exposure adds another level of Exhaustion. The character can survive and recover if rescued, but only magic can restore lost limbs and damaged organs.
