Ahh, it's rewind time. To make it short, this is a recap for the first 10 episodes of the series. Goblin Slayer is still a relatively short serialization, and for one to have to watch a recap isn't going to be necessary unless you're not watching it on a daily or weekly basis, it takes a lot to forget about the key moments of the show for how questionable they are in the first place. As a recap episode, this is really well done, with no annoying reoccurrence, it really manages to pack in a lot of emotion and emits the spotlights on Goblin Slayer and cowgirl themost, making you think they are something big coming up for the two next.
I wouldn't call this a must watch, unless you're too invested in characters and want to see more of them, then give it a go, I for one thought I've got the story on the right tracks, until I watched this recap and managed to pick up a lot of detail I somehow slept off on previously, it really helped explain a lot of things better at the end.
Pretty solid recap at a decent production value if I do say so myself.