Rimebound Heart

Like all undead of a cursed sleeping city, a rimebound heart is glazed in hoarfrost that hides it until it stirs. Beneath the ice lies a severed humanoid heart trailing a grisly snarl of veins. It beats only while it is stealing life.

Without prey it lies utterly lifeless, neither beating nor regenerating, but any living creature within 20 feet wakes it no matter how long it has slept. Every round, each living being in that range needs a 12 or better on 1d20 to resist, adding its Constitution hit point bonus (anyone may use the warrior bonus for this roll). A failure costs 1d10 hit points, which flow into the heart up to its maximum; any surplus is wasted. Life stolen this way never returns through natural rest, only through magical healing. A creature drained to 0 dies, with a 13% chance of rising as a rimebound zombie within 24 hours.

Once awake, the heart beats for a number of days equal to its hit points, losing 1 hit point per day until it reaches 0 and falls dormant again.

The heart cannot move or strike, but while it is feeding it can blast every enemy within 30 feet with a wave of frost for 2d6 damage, negated by a save vs. spell.

Burning it, dissolving it in acid or some similar method is the only way to destroy it for good. It is turned as a mummy; since it cannot flee, a successful turning simply makes it stop attacking unless it is attacked. Poison, cold, death magic, sleep, hold and charm have no effect on it.

Unlike ordinary undead, the heart has no lasting bond to the Negative Energy Plane. A channel to that plane opens only while it drains life and closes once it stops, so it stays animate only as long as its stolen vitality lasts.

Rimebound hearts are wholly artificial, created by black necromancy and found only where their makers have placed them, since they cannot move. The rare spell behind them was devised by a necromancer of a secret academy of the dark arts after studying the sleeping city's undead; the heart was his first such work, and surely not his last.