The "Friends" cantrip (PHB pg 244) has a range of "self", but it also affects "one creature of your choice". Can this creature be one you can't see, such as one behind a door?
This question: What good is Friends? includes comments about using the cantrip against a guard on the other side of a gate, but I get the impression that the caster would be able to see the target in that scenario.
I'm looking for answers based on the RAW; if there's another spell which has a range of "self" but still only effects a specified target other than the caster, that would be a big help for comparison.