Life Transfer has been cast on it, so it will transfer life to you when harming enemies.
Life transfer is a spell given to priests of Fo at 61 faith. It is a weapon enchantment that gives the wielder a chance to gain a small amount of health every time they land a hit on an opponent. The health will automatically be applied to the player's most severe wound.
Healing spells and enchantments grant the healed player a healing resistance effect. This effect is applied based on how much health is healed, and will reduce all further healing on the target from any healing spells or enchantments. This includes healing spells as well as weapon enchantments that heal the player, such as Life Transfer.
The maximum duration of healing resistance is approximately 20 minutes, and the reduction scales linearly from that mark. For example, if you have 10 minutes of healing resistance remaining, you will receive heals at 50% normal effectiveness.