One that can be accessed and worked wish to a great extent, should one be astute.
To invoke their protection on a specific task, you will need a green candle, preferably large and something that will burn for many, many hours. Carve into the wax a serpent wrapped about it, with the serpent's tall nearest the bottom and its head at the top. Between those coils, carve your intention, including what you seek to be guarded from.
Then, ritually dress this candle in ingredients of your choosing, taking from either your own understanding of herbs or from the details shared in this post. As you do so, consider that you are bathing this candle in essence and adding to its form, and when you've completed this process, anoint it in your blood. The prick of your finger will do.
Place the blood on the wick and base, then set the candle alight on a fire proof base, letting it burn either for short durations each day or as one long ritual. When the candle has burned to completion, save a portion of the remaining wax.
Next, you will carve a sigil into this wax representing the goal in question. From there, place the inscribed wax into a cloth bag and begin to carry it with you each day. This will form a protective talisman that can be put to use.
This technology can be used in a number of ways, and the ritual provided here is simple enough to be widely applied. ;)