Ascension literally involves a ritual. In that it is a psudeo alchemical process the Traveler knows for empowering things.

Ascension literally involves a ritual. In that it is a psudeo alchemical process the Traveler knows for empowering things. They can do it without mora, but ironically enough using mora is actually cheaper and far, far, more easy.

Instead of running all over Teyvat looking for reagents that may or may not exist in this world, the Traveler just burns a lot of mora in order to empower artifacts. Weapon and character ascensions are a bit more complicated and require some specific reagents, but not as much as they would otherwise.

All this means is that at one point every character in the travler’s party has had the Traveler invite them to perform in this weird ritual on them involving elemental crystals, pieces of regisvines, hilichurl masks, and things connected to their homeland. They’re not quite sure what they mean by ‘ascension’ but the ritual doesn’t do any harm and in fact makes them feel good, better, stronger. So they don’t really object when the Travler does it again.

- fenerismoon