I have an idea for a prison age(s) that I'd like to talk about...a kind of "prison training age." My basic thought is that perhaps right after Veovis' first escape, the maintainers and writers collaborated on a prison age that could be used for testing...or, maybe it's a series of prison ages that link to each other, that are progressively harder to solve. They might have been used by the d'ni to test both writers and maintainers who were going to create and service prison ages, to hone their skills...
Link to current story if desired by Cyan could be that they know there is something - a tool, a message, etc. - that is in the endpoint of this age or ages that the DRC can't get to. Maybe it's something that can help in the Bahro war. They have reluctantly decided to let explorers in to try and solve the age to get to the needed thing or information, because it's so important...