Protective vampiric sigil

I wanted to know how you would go about constructing a Sigil that protects by means of absorbing energies as a means of sustenance. I’m not speaking of creating a Servitor or thought form , rather each time a certain energy is in proximity it uses it as a charging energy(hence vampiric).

If I would draw the alchemical symbol for salt and write around it with something like this (« energy x within 5 meters is absorbed into this sigil), would that work ?any ideas here ?

Thank you.