Temperature is one mechanic that has a passive effect. In Qud, the default ambient temperature of the world is 25. The unit of measurement for temperature is either T or °, and can be used interchangably. For each object, there are usually four important temperature thresholds:
- Brittle temperature, the temperature an object becomes frozen (by default, this is -100T)
- Freezing temperature, the temperature an object starts to freeze (default 0T)
- Flaming temperature, the temperature an object is set on fire (default 350T)
- Vapor temperature, the temperature an object is vaporized (and instantly destroyed). (default 10,000T)
At the end of a turn, if an object's temperature is more than 5T away from the ambient temperature, the temperature will move towards the ambient temperature by the difference in temperature/50, or a flat 5T depending on which is greater. This means that passively, any temperature change will return back to the normal ambient temperature asymptotically if the temperature is farther than 275T away from ambient temperature (300T or -250T), and that the shortest time to return to ambient temperature is (temp difference)/5 turns.
Forced temperature change
Temperature changes require the object and the heat source to be in the same phase. Heat and Cold resist are the percentage that harmful temperature changes actually affect the object. For example, a 10 heat resist from a mean harmful positive heat increases will be decreased by 10%. "Harmful" temperature changes refer only to a temperature change where it would bring the object's temperature to greater than 50 or less than 25. Heat and cold resist do not change how temperature changes between 25-50T. If the creature has Fatty Hump, all temperature changes are halved, including cooling down when on fire, or heating up when cold.
Reason: Cooling multiplier isn't used anymore. We need to figure out how temperature is calculated again.
Cold is any negative temperature change. Not to be confused with the Cold Damage Type. The following are examples of things that cause decreases in temperature:
- The bite of a
- The depths of
- Freezing weapons
- If hotter than the ambient temperature, being covered in a liquid with a cooling multiplier decreases temperature by a percent amount according to the following formula:
- Overdosing on tonics with a
An entity's quickness is reduced by 50 times the absolute value of their current temperature divided by their freezing temperature (both measured relative to their brittle temperature) rounded down (which means a temperature of -45 will for an entity with default brittle and freezing temperatures result in a quickness reduction of 22) if they are freezing. If frozen, however, they will be unable to move or perform any physical actions that requires moving their extremities but will not have their quickness reduced. Most mental actions, however, can still be performed while frozen.
Heat is all positive temperature changes. Not to be confused with the Heat Damage Type. The following are examples of things that cause increases in temperature:
- Stepping in, drinking, or getting covered in , which increases temperature dramatically.
- Overdosing on tonics with a
- Flaming weapons
Player characters can also fight fire on nearby creatures, nearby objects, and objects in their inventory, unless they are not phase interactive with the target or the target is flying and they are not. This can be done by selecting "*fight fire" in their interaction menu.
By default, firefighting will use the creature's hands, decreasing temperature by -100T.
If a creature attempting to fight fire on itself is currently prone or lacks hands, they will roll on the ground instead, or they can choose to go prone in order to roll on the ground (NPCs will do this at or below 50% HP). Rolling on the ground will decrease the temperature by -200T. A creature cannot roll on the ground if they are phased or flying.
If attempting to fight fire on a hostile creature, the player character must succeed a roll of 1d201-20 (Avg: 10.5) + Agility modifier. If this is lower than the creature's DV, they will dodge the fire fighting attempt. 
- If not specified, it comes from