For my first round, I had two domains with a Yog resource and one domain with a Yog and a University resource. I played the Servant from Out of Tine, who has a Forced Response: After Servant from Out of Time enters play, sacrifice a resource from one of your domains, if able.

Because I like the mixed-resource domain, I would prefer to sacrifice from one on the other domains that has only a Yog resource. This, however, would result in me having a domain with no resources on it at all. Is this permitted? I cannot find any strict reason it would not be permitted, but it seems a bit off.

Any advice would be greatly appreciated.

You can have a domain with no resources attached. There are even a few cards that allow you to create a new domain without any resources attached. Most cards that create a new domain have additional text giving information about immediately adding some resources though.

So what can you do with a domain with no resources?

1.There are some cards that require you to "drain" a domain for an effect (not indicating a "cost"). If that's the case you can use this domain for that purpose, even though there are no resources attached to it.

2.You can of course begin adding resources to it again when your next resource phase comes around.

Ah, that makes sense. Thanks for the heads up.