You can make yarrow ink if you do much handwriting. It’s actual usable ink for sigil magick and petitions.
Simmer a handful of dried yarrow flowers in about a cup of distilled water for 30-40 minutes until it reduces by half and turns deep golden-brown, then strain it through cheesecloth and let it cool. Stir in a quarter teaspoon of gum arabic (art supply stores carry it) until you get a workable consistency. Add a tiny pinch of salt as a preservative.
Dip a nib pen or even a sharpened twig into it and write your intention. Protection sigils work especially well when they’re made from the plant whose energy you’re calling on. There’s something about that directness. Store it in a small dark glass bottle, and it keeps for a couple of months in the fridge.