I've been fighting golbats in the resolution cave for hours, yet I still haven't seen a single crobat! When will crobat come out and let me catch it?

If you are trying to encounter one by itself, then this won’t work. You have to lower its HP as low as you can without knocking it out (try false swiping it) and then use an adrenaline orb. Having a Pokémon with the Intimidate, Pressure, or Unnerve ability helps too. If the Golbat calls an ally that you don’t want, try to knock the ally out with a super effective move. This will make the Golbat more likely to call a Pokémon with great individual stats, a Hidden Ability, a Shiny Pokémon, or the Crobat you are looking for. Once the. Crobat comes as an ally, try false swiping it (use the move False Swipe) and then throwing your best Poké Ball (preferably Ultra Balls or Dusk Balls).