Dark Charms like Hexes are not all evil - some are even used for defensive purposes or in duels like the Twitchy-Ears Hex.

Ingredients often used in spell casting of black magic, hex, and curse spells are pictures, hair, nails, talismans, charms, and sometimes even clothes. Despite advances in science and technology ...

If the target dies before the spell ends, you can use a bonus action to hex a new creature.