I'm playing in a campaign that involves an interdimensional hub of sorts, wherein adventuring parties are given missions and teleported across space/dimensions to the location. Upon completion, in order to return, they are given a spell scroll of Sending by which they contact a dispatcher, who then opens a portal back.
The phrasing of the Sending spell specifies:
The creature hears the message in its mind, recognizes you as the sender if it knows you, and can answer in a like manner immediately.
How are we to interpret this?
For example, suppose a character were to use Alter Self to disguise themselves as someone else, use a different name, forge an assignment, and use that to get to a location of their desire. Upon casting Sending to return, would they be recognized as their "true self", or simply as the person the recipient knows them as?
Is there any means by which an identity can be masked as someone else (or otherwise concealed), specifically in regards to Sending?
Note: There is one dispatcher in particular we interact with the majority of the time who we know well, but there are theoretically others we haven't interacted with yet, if that makes any difference.
Best Answer
No, you can't fool the spell, you have to fool the target another way
The spell Sending specifies that recognizing the sender is a part of the spell's function, and nothing in Alter Self would change that, as it is appearance based.
Sending (as you quoted yourself):
So if the target knows you, not just your appearance, then it will know you sent the Sending. What you look like at the time is irrelevant, the spell functions as it says it does.
Alter Self:
Nothing here says anything about disguising you in any other way besides visually. It does say the sound of your voice changes, but Sending makes the target hear the message in their mind, not with their ears, so changing your voice doesn't affect that.
Now, by what you have described, you'd have to have used a dispatcher who does not know you to begin with and to have already disguised yourself before speaking to them, so when the Sending gets back to them, they will know it comes from the same person they sent out. Basically, you have to fool the dispatcher, not the Sending spell.
To be clear, if your name is Bob the Baker and you have an alter-ego as Skinny Larry, and you cast sending to someone who only knows you as Skinny Larry, Sending will not out you as Bob the Baker, they'll know the Sending came from the 'you' that they were introduced to.