Detect evil (Divine sense) wouldn't register anything for her. It merely determines the presence of a celestial, fiend or undead. We know that she is none of these. This still wouldn't determine whether she could be trusted or not.
Oh, My apologizes I forgot Detect Evil got nerfed in Dungeons & Dragons 5e compared to other editions.. Sighs, well so much for that consideration.
Edited: Thomaslee on 26th Aug, 2017 - 7:07am
Yeah, sorry, as the others have said I don't think my level 2 Paladin has anything for this. I've tried Divine Sense and it didn't even pick Irdeith up as 'strong good' so I don't think it would pick up anything a tall.
I've been trying to think of other ideas to help such as "Velon has a vision that Zarra is important and will save another in the party and insists she must come" but it doesn't really work since he has never had another other such visions.
----------------------
*Please note that I am taking a group backpacking in VT today/tomorrow and likely will not have cell service. I should be back tomorrow evening. Sorry if I miss any chances to post to help with this. The Dungeon Master can play Velon for me if necessary and if there are any group votes on having Zarra come or anything like that please consider Velon as supportive of that, although a reason would still be best for ongoing role playing purposes.
In regards to the secret mission thing. The principle danger there is in either having the cult know you're coming, or other hostile groups know to wait for you when you leave the mere.
Zarra does not present a threat with either concern at present. Though once you tell her of the mission it would not be prudent to leave a stranger behind.
In regard's to Velon's Divine Sense, it is attuned to pick up otherwordly energy, not the ethics of a person. It would have picked up Irdeith as strong Good had he been a cleric or paladin of bahamut rather than a sorcerer. When the clerics in the group get to higher levels, it will start picking them up as well. But no, it is not usually useful in regards to being able to trust a stranger or not.
Edited: daishain on 26th Aug, 2017 - 1:33pm
The detect evil/good/etc spells? Yeah, they're gone.
I have to say, I'm not entirely sorry to see them go, they make it a lot harder for mysteries involving people to last. "Who killed the Queen?!" *Cast Detect Evil* "Uh, I'm no expert, but maybe you ought to take a look at the Queen's brother in law, his aura is about as wholesome as a rotten onion." *an hour of intense investigation later* "Yep, he dunnit, mystery solved"
Edited: daishain on 26th Aug, 2017 - 4:20pm
I have to admit, I think we went about integrating Zarra into the group in a manner that would leave quite a few of us uncertain and one or two of us downright against it. So we have our two spies, who should probably be among the most leery being all peaches and cream. That doesn't seem to make sense to me… that's me the player although Fay would be a bit confused too. Why would they want her to go with them? Why wouldn't they just do what Paul said? Or, since she doesn't know the plan, simply bid her goodbye if the group is too squeamish to slit her throat, which most probably would be.
As far as Zarra not being a threat, the fact she is a Drow presents a threat. We are looking at this from a 2017 perspective. Imagine this from your character's perspective. The Drow are the most evil of races that enslave for pleasure and kill those whom they capture that they don't enslave. And this is a well known fact. I thought there'd be some role playing on her part to try and join us or convince us of her intent. Not us bending over backwards to ask her to join our mission.
Heck, what is she doing here? Maybe she and the Drow are on Tiamat's side in this. She hasn't even really told us why she is here. Why was she travelling here? A Drow says this what happened and we all nod our heads. That would be like me listening to a guy walking through the hills of Afghanistan with bomb making material and Al Qaeda literature say he was a sheep herder and believe him and then ask him to join my patrol.
All that said, I guess it is what it is at this point. We've invited her along for God knows what reason. Meta tells me everything will be fine. But Fay doesn't have the advantage of Meta and Lia certainly doesn't and would be the most apprehensive.
Edited: Abnninja on 26th Aug, 2017 - 4:33pm
Cratol is just playing on his beliefs. He is also going from his memory of Sar'ai and how she was and the trouble they got into together that caused a rocket to be prematurely launched. So he may be a bit more accepting of a Drow that the rest of the group. This is the reason for talking to her and seeing if she would be a fit to join.