The root of the term ‘redemption’ means= ‘the act of repurchase, as of something sold; recovery by repayment, as of something pledged.’
Redemption is not so much ‘deliverance from’ sinfulness, but more a matter of coming good in the end through a process that undercuts evil by excavating the good buried in it; by uncovering the ‘grounds’ why good lapsed into sin through evil’s power, it finds something more powerful than evil to stand on.
This is the immeasurable change in the depth of the heart effected by Christ’s Descent into Hell.
This breaks the devil’s power.
In saving, things in darkness – human and demonic – are brought into the divine Light; in redeeming, the darkness itself is plumbed, or searched out in depth, and changed at foundational source by the divine Fire. Thus, heaven really is born from hell.
Christianity as a whole has not yet penetrated this great mystery.