The advantage of a high-density energy beam is that it can be infinitely stacked and focused to exponentially increase its power, even reaching the level of a stellar surface. No matter what kind of creature it is, none can withstand such intense heat, and instantaneously turning into a plasma state is the only outcome.
Even if there are some losses of the constant starlight crossing long distances, with such an aggregation, seventy to eighty percent of the energy is still retained. Moreover, due to total reflection, the slight loss is negligible, and the generated heat is insufficient to offset the extreme cold brought by the cosmic darkness.
The only trouble it brings is light pressure, coupled with the gravitational field interference of the Seventh Planet, forming an effect similar to a stellar sail. A slightest mistake could lead to the total reflection mirror's position deviation.
