Quote from Muramasa
A flying Black Dragon that spits miniature Black Holes would be really nice.
You can do the deed and erase the evidence at the same time.
Dragon's with high intelligence should be able to do that. Since you're looking for something that you can control, though, I think you're not going to be able to work things out. After all, a dragon that spits black holes would probably be liable to collapse on itself from a sudden impact.
This signature was recovered from Hades to serve in my rotting armies.