If you look in the Atk tag for it, you might notice a selfHealFactor property. This is the percentage of damage done that gets restored as health. It's limit is your max health, because it doesn't do anything to raise your health cap.
It's worth noting that setting it to a negative number does nothing.
Likewise attacks like Soul Suck use the selfFocusFactor property. Like selfHealFactor it determines the amount of damage or shielding that gets restored as energy.
It's worth noting that you CAN use a negative number with this property to add a variable cost to an attack, such as in Transfer.
If there are any more questions you have, if I can answer them I will.
