by the immortal powers

prepositional phrase2

1. •
   (informal) Expressing emphasis.

   • By the immortal powers, if you had let Rory put a few slugs into the old buss, he'd have settled the baronet's hash altogether. — 1885
2. •
   (informal) Expressing surprise.

   • 'You, of all men, by the immortal powers!' he proclaimed enthusiastically. 'What piece of luck brings you this way, Max?' — 1927