There was another benefit to the tattoos, that Belladonna considered as she examined the Orcs set up.
If you had powerful enough ingredients to hold the burden, theoretically you could place a high level enchantment on a low level individual, or even someone utterly devoid of magic, and still have them be perfectly able to cast the spell without any risk of blowback or bodily destruction.
The only issue in that would be the mana requirement, as an individual like that could not supply the spell the right level of mana to activate it. But such an issue could be fixed with charged Mana Crystals, like one used for actual magic circles or ritual casting.
It would probably not be worth it, but the option was there. Especially if you wanted to make use of disposable individuals, load them up with explosive enchantments and turn them into magical sappers.
A rather disturbing thought, if she did say so herself.
