Childe observes with a minor kind of awe, particularly as it seems as if it draws from nature itself. Leylines and clusters of raw elemental energies are familiar sites to him in Teyvat, but observing someone casting magic without a vision is not. Of course, the Traveler can, but ... even that's different from to what he's looking at right now.

The sensation of this magic as it heals is strange, as well, but not unwelcome. Even if it can't heal him entirely, he'll still be plenty grateful as this is not a leisure he often gets after a battle. It'll be more than enough to have the other acting like nothing's wrong, anymore, which is all the needs.

When the magic ceases, Childe goes to check his shoulder injuries from his fight with Caitlyn and then the ones at his back for where Hubert stabbed him. He's not sure if it's completely healed, but it seems pretty damn close if not with a little soreness still lingering. This is easily more than he could have asked for. Which is why the Harbinger will look up at the older man with a surprised but also grateful expression. "...Amazing. Thanks."

Someone going out of their to patch him up— for any reason— it's not something that happens, so he has to make sure it's known that it's appreciated. Now, he's curious, though, and adds a question into the mix almost immediately after expressing it.

"Is that a common ability in your world? I mean, I don't think I've seen a healing magic this potent before."