I craft from another world has crashed in the middle of a nearly worldwide conflict being fought on 1880s Earth. This Visitor was first found by the German Empire. Since then he has been aiding the Germans with technological advances which has given them the upper hand in the conflict, much to the chagrin of the Nefarious Professor Nightshade, whom until then had been their main weapon supplier.
Little do the Germans and their allies know, but heir Visitor is actually an intergalactic space criminal and key player in a much wider galactic conflict. This Visitor did not crash, but was shot down by this little fellow (not little, he's about 38mm). He has now presented himself to the British Empire as the Emissary, and promised aid to battle the Visitor.
New technology harnessing X-matter. The Destructo-Ray.