Creating a Climbing System for Mobile Entities

So, the best way I can really describe this is to compare what I want to do to the system used in Shadow of the Colossus, where the PC is able to grapple to a larger entity and follow its movements as they attempt to climb the creature. I’ve had the thought to do for a small project of my own, but it’s such a rarely used mechanic that I haven’t been able to find any insight on how to create such a system. Was hoping that someone would be able to point me in some direction that would help figure this out. Thank you.