Weapon (longsword), unique (requires attunement)
A longsword of white steel, with glowing ice-blue runes etched on one side. The blade is cold to the touch and is covered in a rime of frost, though which the runes can be seen. The hilt is wrapped white fur.
The runes are in Suloise, and reads Coldheart. The fur of the hilt is winter wolf fur.
Even when you are not attuned to Coldheart it counts as a magic weapon and deals an additional 1d8 cold damage on a successful hit.
In freezing temperatures, the blade sheds bright light in a 20-foot radius and dim light for an additional 20 feet.
If you are attuned to Coldheart and have it on your person, you have resistance to cold.
Cold Magic. Any cold-based spell or effect you cast gains a +1 to any attack roll required as well as to any spellcasting check and save DCs. Each damage dice of a cold-based spell or effect you cast gains a +1 to it.
Extinguish Fire. As a bonus action, you can plunge the sword into any nonmagical fire, extinguishing any fire within 20 feet of Coldheart or portion of the fire if it is larger. You can also use this to attempt to dispel magical, psionic or similar fire effects as if you cast dispel magic with a 6th level spell slot and a +5 spellcasting ability, except that its effects extend to other supernatural effects. Once used this property cannot be used again until an hour has past, and shares a recharge with Counter Fire Effect_.
_*Counter Fire Effect.* As a reaction, while wearing Coldheart you can attempt to counter any spell, psionic power or similar effect that deals fire damage that has you in its area of effect as if you cast counterspell with a 6th level spell slot with a +5 spellcasting ability, except that its effects extend to other supernatural effects. For effects that do not have a spell slot (or equivalent), such as a dragon’s breath weapon, make a spellcasting ability check using the Save DC of the effect as the DC of the check. Once used this property cannot be used again until an hour has past, and shares a recharge with Extinguish Fire.
Paired Set. Colheart is paired in a set with the sword Fireheart . When both weapons are attuned to and wielded, it gains additional features.
The additional cold damage is increased to 2d8.
Spellcasting ability check for both Counter Fire Effect and Extinguish Fire increases to +6.
The spell slot cast for both Counter Fire Effect and Extinguish Fire increases to 7th level.
Any object or construct that suffered both fire and cold damage from both weapons suffers an additional 2d8 magical bludgeoning damage.