In the Archduchy of Tatenae ruled by a Feudalist, a character must undergo a Trial by combat.
He has been framed by A collusion of guilds - uses resource control for leverage - and if found guilty of Murder, his punishment will be Baleful Polymorph. The prisoner permanently changes into a small animal. One of my favourite D&D modules is Castle Amber. Wouldn’t it be a neat twist for the central garden to be the prison of several banished beings changed into the form of small animals? If the subjects fail their second saving throw, they even gain animal intelligence, in effect becoming just another creature in the garden.

Archduchy - The dominion of the archduke, who is higher ranking than the grand duke, but still beneath the king. Usually a member of the royal family in line of succession.
Feudalist - A political and economic system of Europe from the 9th to about the 15th century, based on the holding of all land in fief or fee and the resulting relation of lord to vassal and characterized by homage, legal and military service of tenants, and forfeiture.
Trial by combat - Fight to the death, winner is innocent