This icebrand greatsword was one of several dozen forged in the third age by the early human slaves of the frost giant jarls. Created as weapons that wouldn't be turned against their masters, this frostbrand was most famously used to end the life of the elven explorer, Alaesti Firebearer.
Alaesti allied herself with the human servants of the frost giant warlock Jökultönn. She spent months teaching the men basic magics as well as forging a set of eight flametongue longswords to fight the frostbrand swords wielded by the giants and their servants. Unfortunately the rebellion was cut short being infiltrated by loyal servants of the giant. Alaesti Firebearer was slain by the frost giant warlock Jökultönn, weilding this frostbrand, and the rebellion was quelled. Jökultönn did not escape unscathed however as the wounds from Alaesti's spells eventually took his life. Jökultönn's rule was short and harsh, continuing after his death, his spirit persisted, imbued into the very frostbrand sword which took the life of his greatest enemy.
In the late third age, an elven army following the trail led by descendants of Alaesti Firebearer invaded the lands of Thrym, slaying many. They recovered three of the eight flametongues along with the sword containing the spirit of Jökultönn. The sword was trusted to the grey elves of the city of Mith'Taern. Sensing the great evil within the blade, they struck it upon a peak in the mountains of Yod, to be forgotten by the ages.
In the fourth age, the sword was rediscovered by Geshran Herat. Weather beaten and tortured by solitude, Jökultönn had forgotten his own name. Geshran chose the name Rimebrand to signify the swords unique nature and accepted the blades assistance in slaying the resurrected hero-deity Valotha the Venimous. The greatsword was carried by Geshran into unknown realms while he accompanied Parun's fellowship.
The fifth age has seen little of this historic blade, although he is still apparently carried by his friend, Geshran.