On top of upgrading your characters the Dendrobium are often used in Genshin Impact, while not that hard to find you'll still need a lot of them so here's a guide to where you can get your hands on a bunch.
Dendrobium Location genshin Impact
You will be able to find Onikabuto on these two islands:
- Yashiori
- Kannazuka
If you're looking for a more precise location for all these Onikabuto I'd advice checking the official interactive map where you'll be able to zoon as you see fit.
You can find the map on the Hoyolab website here.