Plate armour, made for Asildur by Elverandil, modified by the Dark Powers
When Asildur made his ill-judged attempt to bargain with Dark Powers for power against the Dragon & was made a Death Knight, his bright armour was likewise tainted & empowered.
A demon of some sort was bound in it & a shred of Asildur's essence also remained, whispering occasionally to the wearer. This was corrected in 1605 when the Mastersmith reforged the armour and re-enchanted it to remove the taint.