Or, you could add 2 artifacts:

One prevents the enemy from surrendering but allows them to escape.
The second prevents the enemy from escaping but allows them to surrender.

Together, the effect is similar to that of the Shackles of War (but only in one direction).

There's an atmospheric justification for this :)

The first artifact prevents diplomats from confusing the hero (you could create a dialogue box like "do you allow the enemy hero to surrender for such and such an amount?"). The artifact could be named something like "Amulet of Impartiality".

The second artifact essentially allows escape only for money, i.e., makes the hero greedy and calculating; something like a "Merchant's Cloak" would be suitable.

Another advantage of these artifacts is that they occupy important slots. That is, unlike the Shackles of War, you'll have to sacrifice stats or something else.