Hexes are unique compared to other magic spells in Dark Souls 2. They use intelligence and faith both as resource pool and require Staff and or a Sacred Chime depending on the skill that is being caste.
That’s not it though, the high damage dealing hex spells even require you to sacrifice few souls in order to get the best out of them. Due to the varied factors hex magic is dependent on; Hex Spells are quite difficult to use effectively but are useful nonetheless.
It’s a school of magic that should only be opted by the skillful players otherwise you may not be able to get the best out of these spells and may not know which spell to go with under different situations.