Amulet of the Coldfire Phoenix

Wondrous item, very rare (requires attunement)

A blue pendant in the shape of a phoenix clutching a shimmering blue orb hangs from this leather cord. While wearing the necklace, you emit a frigid aura that grants you and creatures of your choice within 10 feet of you resistance to cold damage.

In addition, when you are reduced to 0 hit points while wearing the necklace but not killed outright, you can drop to 1 hit point instead. When you do, you gain 25 temporary hit points. If a creature hits you with a melee attack while you have these hit points, that creature takes 25 cold damage. Once this property has been used, it can't be used again until 3 days have passed.

"I fear not the fires of Hell but the cold loneliness that death may bring."