If you are in need of some rare and hard to farm materials, there is a high chance that you can get that material by combining other smaller, and easier to get versions of it, all you need is mix some materials and convert them into the ones you need.
How to Convert Materials
Material Conversion is a way to transform easier to get materials into a material that is harder to get, to do that you will need to spend a higher quantity of the easier to get material and get a smaller number of your target material.
For Example: Let’s say you want to farm Spectral Nucleus for your Baal or Kokomi’s ascension, knowing that specters are annoying to deal with it would take you several hours of farming to be able to get enough Spectral Nucleus, but along your journey you would’ve dropped many Spectral Heart, if you combine 3x of them you will be able to get 1x Specter Nucleus.
To do that all you need to do is go to the closest Crafting Bench, scroll down in the crafting material list until you find the material you need, once you do combine 3x of a lower tier material to get one higher tier material and you are done.
This is a great way to get the needed materials for a character or weapon ascension as fast as possible, note that this is not recommended if you are new as you will need every material to build your team and weapons slowly, but if you already have all you need and all you want is that ascension and you have a lot of materials just sitting then go for it.