How do you know a witch when you see one?
According to Catalan witch-lore, it's easy: you look into the eyes. Witches' eyes are distinctive.
(Catalunya's witches—bruixas—are a fascinating lot. Their witch-marks look like two horns, crossed. They dance naked a lot, especially on Midsummer's Eve, especially on Montserrat [Sawtooth Mountain] and Pedraforca [Forked Stone], the two sacred Sabbat Mounts of Català.)
Look into the witch's eyes.
In one eye, you'll see a double pupil.
In the other, a deer's antler.
Friend, can you read these runes?
Obviously, the double pupil is for the Second Sight.
As for the antler in the other, well: I'm sure that you don't need me to explain.
You know Him when you see Him.