I translated this as "Therefore death is nothing, since the nature of the death is held by the mind."
Nihil igitur mors est, quoniam nātūra animī habētur mortālis.
Wouldn't mortalis have to be the direct object since natura and animi are already ablative and genitive respectively? Why is mortalis not accusative or ablative, given that it only makes sense for it to be the direct object of the passive verb habetur in this context? How do you suggest that I translate this?