He has found three references to the term. All of them are in manuscripts over a thousand years old. (Actually, copies of manuscripts where the original is that old.) None are in infernal, so they are missing the context that would most obviously clarify the meaning of the phrase.
Two of the references are very brief and clearly expect that the reader knows what the przywrócenie niszczyciel is. They seem to indicate that the przywrócenie niszczyciel is a person who will live at some time in the future.
The third has more detail. The przywrócenie niszczyciel will arrive and play a crucial role during some major change or transition. The transition will happen regardless of his (her?) actions, but the przywrócenie niszczyciel will be crucial in determining how the change happens and what direction it takes. There is also a vague reference linking the przywrócenie niszczyciel with the Fulcrum.