Cold is one of the 7 elemental damage types.
Cold damage is usually the second elemental spell a mage learns, often while still on Silan. It is generally the preferred type of damage against kitin until the mage reaches level 125 and can learn the racial damage types (fire, poison, shockwave and electric). And even after that Cold remains the best spell against many kitin.
Most kitin have no protection against Cold magic; exceptions are Kincher and Kirosta, but even against them Cold is no worse than any other spell. Only against Kinrey are you better of using racial spells. By contrast, over half of all animals and intelligent plants have protection against Cold magic. All creatures in the Prime Roots also have significant protection against Cold.
Protection from Cold
Cold may be used against you by other players in PvP, or by homin casters from bandits or tribes. In particular, Cold is often used by the NPC healer guards at outpost battles. Furthermore, Stinga and Gibbaï are also capable of casting Cold spells.
All player characters have a default 10% protection from Cold damage. You can protect yourself against Cold damage further by wearing jewelry that gives additional Cold protection. You can have at maximum 70% protection.
You can also increase your chances of resisting a Cold elemental spell by wearing jewelry that raises your Lakes resistance.
Non-magical Cold damage
Many bandits and tribes guards have random elemental damage added to their melee and ranged attacks, including Cold. If you're hit with Cold damage that way, Cold protection will decrease that damage, but Lakes resistance will not help you resist it.