My Advanced Alien Civilisation has the ability control the rate of fusion within a star. They do so by selectively (and very gradually!) altering the electron degeneracy pressure of regions within the star in a handwavium-based process.
Now this technology can also be used to achieve nucleosynthesis and eventually to create black holes from non-stellar quantities of matter.
The question is, (broadly speaking) have I missed any other potential applications of this technology? I don't need specifics; I'm just trying to make sure I've covered all bases.