That's an interesting topic
If you attacked someone (or someone attacked you) then it is resolved through ransom. If you escape, the ransoming party will complain against your clan/tribe. It's a matter of honor but it's also a matter of civilization. A lot of comments are about how could we prevent dangerous PCs or NPCs (especially those loaded with magic) from escaping? That is not the point IMO, the point is what happens if they do and their clans rejoiced at this? It would be Chaos: no one would take hostages any longer, it would be an endless cycle of killing and revenge. The ransom legal system is about avoiding this, it's about having a more civilized society. If you lose to the Greydogs your family, your temple and your clan leader will pay (then you will owe them but it's called Loyalty). Okay, maybe you are planning a rematch but you won't be planning on killing anybody, you'll plan to take another hostage to get even; and even if it sets a cycle hostage ransoms this is manageable (as opposed to a killing spree). This being said, alright you escape with your powerful magic. What happens when the Greydogs complain? You dishonored your family, your Temple (therefore your gods), your tribe, your clan. Are you better off? Far from it.