If it can be created and destroyed then it is not energy and shouldn't actually be able to harm anything because that would require a form of energy which can transfer, and if you can create something and transfer it into a different form of energy you just created energy and thus defied science, universal balance and pretty much every scientific theory published since the introduction of the Law of Conservation.
Even if you can do that, you still have to transfer it into a different energy for it to do anything (It HAS to transfer, or its not going to harm anyone or power anything or... Well, pretty much anything except exist, and for the purposes you are using it for that's not going to help. Energy production is done through transfers) The Triarii manipulate energy, their abilities working through transferring energy. As a result, all they are doing is manipulating what results from the magic. Whether they are manipulating the magic or not is irrelevant, if they remove the kinetic energy it won't move, remove thermal energy it cant burn, remove electrical energy it couldn't electrocute etc. They are rendering it harmless, they do not need to manipulate magic to do this.
Thus, what I did breaks no rules, is sort of commonsense for a species which manipulates energy and is at least somewhat im line with some form of science, which is more than I can say for most anything else that's been done
If you are going to use science to tell someone they cant use a black hole as a wormhole, then you can expect it to be used to argue against this magic thing. (I am not in support of black hole wormholes, I just want to point out this is pretty much the same thing in a different dress)
Even if it does disobey the laws of conservation entirely and magical energy can't be manipulated for whatever reason, I think I have provided enough to show that my post still makes sense when removing those two things completely
tl;dr Rudimentary Physics, common sense, logic