Possibly this one.

"All right, I've been told some very contradictory things about you. The local custom is to nod your head like this for 'yes' and shake it like this for 'no'. Do you understand me?"

Nod!

"Are you sometimes unable to speak?"

"No, I can talk, just not your language."

"Did you pray for the Precursors to give us this food?"

"Precursors??"

He smiles predatorily. "Some people tell our creators about their problems in the hope that our creators will hear and take pity on them. But not you, I take it. Did you teleport here?"

...will this guy shake his hand if he holds it out.

Sure, though by default he'll do it with gloves on.

If gloves made touch range spells impossible then operating at the Worldwound in winter would be nigh-impossible!

"Share Language."

Erol gets everyone's attention and, as though this makes perfect sense, tells them he perceives himself to miraculously speak a new language and is going to tell their guest to clap his hands three times in that language as a test. And then he does that.

"That would also have worked before when I just had Comprehend Languages up," Blai remarks, clapping thrice.

"Assume I know nothing about your powers and explain them from the beginning."

"I am a cleric of Iomedae, Lawful Good goddess of defeating evil. She grants me a new complement of spells within the limits of what clerics, generally, can do, and within the limits of my personal ability, every morning at sunrise; I am powerful enough to cast spells up to third circle, and spells in general range from zeroth to ninth circle. Comprehend Languages lasts a bit less than an hour, Share Language all day; I prepared more than one Comprehend Languages but only one Share Language this morning. I can also heal, it's a primary capacity of clerics, either in a burst or with touch-range individual spells."

It's the healing that decides him.

"You are in Haven City. Haven City is besieged by metal heads - creatures of dark eco, who hunt and kill and destroy all that they can find. They have nearly ended civilization on this continent already. There is nowhere we can fall back to if they breach the wall - nowhere we knew of before you appeared. If you're going to vanish as you appeared, let me round up some civilians for you to take with you - otherwise, tell me more about your healing."

"I'm not powerful enough to vanish. - also I don't know what dark eco is. Basic healing works by diverting positive energy, which heals living creatures and harms the undead. I can do the thirty-foot burst twice in a day; it's most efficient in a specially designed room that can pack as many people as possible into that radius. I can use any of my spell slots for an equivalently powerful spell that does the same thing. It's very good at injuries and does next to nothing for disease, poison, or infection, which I can prepare separate spells for; I also have access to spells that will cure blindness and deafness in damaged but present eyes and ears, but I am not powerful enough to cast the spell that will restore any completely detached or destroyed body part."

He considers his, realizes he didn't translate "eco" for some reason, then realizes he can't.

"You're not aware of a building block of the universe that can be green, red, yellow, blue or dark - your healing doesn't use a green substance, does it?"

"It uses positive energy, which looks white more than anything, when you can see it."

"Is there negative energy that looks purple?"

"It's black, when it's a color, but there is negative energy, which animates the undead and harms living things."

"I see. ...Did your 'Iomedae' grant you the 'spells' to cure blindness and deafness today?"

"No, I didn't ask for it this morning. It would have displaced the food one; I can only cast one freely-chosen spell of that power per day."

"Ah. I'm sure you can't give a definite answer on the basis of three sentences about our strategic situation, but do you have a guess as to what would be the best use of you?"

"Healing, most likely, especially if you don't have any other clerics - if you have a hundred it can make perfect sense to send us into battle so that while some die others can become stronger by surviving the risk, but with only one that is far from a clear win. I also think it requires less context on my part to be confident that I am not participating in something Iomedae would not countenance."

He makes a face at that last thing. "Do tell me what Iomedae wouldn't countenance doing to keep our children from being eaten alive."