Ice Blades

Ice Blades are extremely rare blades that can be found in once populated regions of the extreme north in the arctic circle & surrounding tundra. A few are also found in high snow-capped mountainous areas in ancient icy ruins.
Magic in nature, ultra-rare ice deposits are found around these sites. Why this is is unknown though some mages & clerics pick up residual traces of magic & elemental power in these regions. The working theory is that the strange ruins that are here are the remains of a lost civilisation, and the ice is one of the remaining types of ariefacts of them. The theory also takes in the idea that maybe the civilisation had access to elemental magic & maybe even elementals too.
It is a surprisingly durable material that can be worked by a master smith with little of any fire used. It can be mined & moulded with a specific set of heated tools and plenty of grinding into shape. Usually mounted within or on metal in general, to help off-set the hardness of the ice, it's known to hold an almost perfect edge that rarely dulls.
Unfortunately the working can lead to failure regularly with the original techniques lost, and many smiths haven't the full skills to work it. Some Goliaths have the skills to work it, and get an perfect sharpened edge on it but the generally don't speak of how to do it.
The Goliaths themselves sometimes speak of the ice being the bones of water-based elementals especially ice elementals & golems. They were created by ancient giants who worked with the elemental planes and regularly summoned elementals into the world being taught how to work the ice & imbue it with magic. Finding the elements of the earth & water in the form of ice made the best weapons & armour, the giants taught a 'slave' race to crtaft many items for the giants. Unfortunately, the 'slave' race rebelled and destroyed the giants or drove them off. Living in the old giant empires in these regions, they made many of the blades & armour to fight off enemies that arrived later. Unfortunately they didn't survive in great enough numbers to hold on to their holdings and eventually dwindled. Rumoured to still exist in cold out of the way places there is the risk of encountering them.
The only thing is the treasures & the ice blades that attract adventurers to these old ruins.

"I've encountered one of those blades in my life. Mounted correctly for the hardness of the ice, it'll almost cut through adamantine. Will go through near everything else with the sharpness of the ice. Attracts the wrong attention though, lassie. You'd be surprised how many Goliaths show up looking for one of them blades when one is sighted."
Childrec Ludgher talking in the inn in Eschbach.