Soul Stone (Equivalent Exchange)

Crafted with glowstone dust, lapis, and Dark Matter.
A powerful gem enhanced by the souls of the underworld, the alchemist can feed it redstone to draw life force from it. When activated, the Soul Stone will constantly attempt to give the player "immortality" at a rate of one heart per second. When left clicked, the Soul Stone will simply heal the alchemist for a single heart. When used against a mob, the Soul Stone will heal that mob for a single heart.
For every single heart healed in any of the above methods, 2 redstone dust is consumed.