Weapon (longsword), artifact (attunement)
Rimefire is a sentient, magic longsword with runes in Giant on either side. The red runes read, "My passion burns," and the blue read, "My rage runs cold." You can attune to her to gain the following benefits.
Aurora's Blessings. You gain rapport with this sword as you accomplish various tasks. These are divided into levels as follows:
One with fire. You have a +1 bonus to attack and damage rolls made with this magic weapon. Rimefire becomes a sword and may communicate with you, though only through carving runes into a block of ice with which she is embedded. The sword deals an additional 1d4 fire and 1d4 cold damage.
Fire and Ice. In order to achieve this level, you must slay both a fire and frost giant: You gain counterspell, which may be cast a number of times a day equal to your proficiency bonus, regaining all abilities to do so each day at dawn. You gain a +3 to any check made as a part of this spell. This spell is always considered a 3rd level spell when cast, even if you could cast it at a higher level. If you are not wielding Rimefire, you lose access to the spell. She may communicate simple telepathic messages to you, one or two words at a time.
Royalty. In order to achieve this level, you must attain a crown and lands, and name yourself King/Queen. Rimefire deals an additional 1d4 radiant damage and the area in a 15' radius around the sword is illuminated with bright light and dim light for another 15'. When sheathed the light is extinguished. When you counter a spell using counterspell, the sword gains charges equal to the level of the countered spell. When you hit with a melee attack with this weapon, you may expend a charge to deal an an extra 1d8 of fire, cold, or radiant damage. The blade can hold up to 9 charges at a time. Every day at dawn, the number of charges is halved. She may communicate with you telepathically without any limit on the length of the message. Her voice seems to originate from the polished gem in the hilt and resonates through your mind.
Sentience. Rimefire holds a neutral good being. She has an Intelligence 14 (+2), a Wisdom of 16 (+3), and a Charisma of 12 (+1). When sheathed, she can perceive all that you do as though she were in your space, otherwise she has 60 feet of darkvision. She is telepathically linked to you, and if embedded into a block of ice, may carve runes onto it in Giant. She can speak and read Dwarvish, Common, and Giant. She was once a Mul Princess named Aurora and was to inherit a city before frost giants attacked. She had the city's forces hold them back using guerrilla tactics while she led a small force to request aid from a clan of fire giants at a nearby peak. They agreed to assist her against their natural enemies. The frost giants were repelled, and the fire giants demanded the city as payment. Without time to deliberate, they began to attack anyone in "their" city. The woman that Rimefire once was ordered her remaining forces to hold them at bay while the civilians escaped. She led the staggered retreat, fighting giants until the populous was far enough away, retreating, then fighting when the giants were in reach again. This was done until everyone living had escaped. When the battle was finished, she returned to her people, but succumbed to her wounds. Her will to protect her people, and her loathing and hatred for the giant tribes that had caused this tragedy mingled, and were the catalyst to her mind and spirit merging into the blade. The Eldrich Knight that she once was ceased to be, and the blade rimefire was born, the runes etching and burning themselves into the blade.
Personality. Mournful on the surface, she is seemingly still in shock at being a sword. Though she is unsure exactly how long it has been, she wants her kingdom, small as it was, to come to be again, even if she's not the one leading it. As such, she wants her wielder to be deserving of the throne. In time she will have a friendly, almost sisterly relationship with you, and offer advice and council when asked, and sometimes when not. If the wielder does evil or does not go out of their way help others, Rimefire will wake them up to have an argument at dawn.