Weapon (any melee weapon), Common
Here the cosmic steel weapons are ones forged by using the mysterious black metal which does not come up from this particular world, simply it is having arrived here by a meteorite or else some other means. However the anomalous qualities of the stuff shall make it ideal for being forging in the weapon, anyway.
Fortitude of the Stars: Here the cosmic steel is the nigh indestructible; usually, this weapon could only be destroyed by the magical means such as by the disintegrate or else by the wish spell.
Conductive Inertness: The Cosmic steel weapons are feel cold to the touch, and it can not be conducted the heat or else change the temperature by any means.