You have to come up with your own tools. Many old games used self developed containers and graphic files which could only be viewed by their own tools.
With a lot of debugging and decompilation you might figure things out and be able to write your own viewer or plugin for a viewer.
That's how we did it for Exult, Pentagram etc...

Talk to Malvineous and he may add it to his awesome level editor/modding tool that supports quite a few games already. The tool is called Camoto, it's open source and he is actively developing it. If he can reverse the proprietary formats and there's a possibility to edit levels then I don't see why this game shouldn't be a part of Camoto.

Link: http://www.shikadi.net/camoto/