Calling it now: Ruby's parents are from space/the future and they die. The woman who dropped Ruby off is Ruby from the season finale.
The episode was entertaining but I'm not sure how I feel about actual magic in doctor who. Even the witches from the Shakespeare episode had technology. Genre shifting an entire show is certainly a choice.
This was definitely more of a character episode than an adventure, with the bad guys taking a backseat and then just disappearing. If unit could have shot the ship with a laser and the episode ends the same then it's a bad resolution.
Tbf, they called this out as it's own technology. The witches had song technology, and these goblins have coincidence/"string" technology. Seems in the same spirit to me.
Also, Unit wouldn't have been able to fix the timeline or save the babies with a laser.
I'm specifically referring to the way the doctor kills the goblins. If the job could be done with a laser gun then it's not an interesting solution. It would have been better if the Doctor played by whatever magic rules the goblins live by and turn it back on them, maybe tricking them in some way. That would have made the episode end like an actual fairy tale, if they're going to bring fairy tale monsters in they can actually use that to their full potential instead of just "blow them up".
I would have also preferred a solution that involved using their own weird logic against them, but using mavity mitts to pull down the ship and impale the goblin king on a church spire is at least unique and unexpected.
Magic I can pass off as just weird science that we don't have the language to explain yet, just like the Not-Things from the space beyond space. The goblins weren't all that different from the reapers that eat paradoxes.