While it won't be available until this December, you can go ahead and pre-order the first Diablo 3 Amiibo for Switch: the Loot Goblin! From the description, it looks like this particular Amiibo opens up a portal to riches. What kind of riches? Well, we don't quite know yet, but hopefully we'll hear about the details soon.
I was hoping for D or Tyrael but this makes sense.