Look forward to reading more!
I had actually written some other things that for whatever reason didn't post :\
Anyway, the danpyr homeworld has plant equivalents in the form of biocrystals that use their star's light and elements in the environment to grow, as well as storing energy for later. While most creatures on the danpyr homeworld can derive some energy from their home star's light directly, they have an easier time processing it from the biocrystal plants, or other creatures. Most creatures on the planet also only need to ingest small amounts of matter, unless they are actively growing or healing from a wound or illness, or carrying young. Microorganisms and other decomposers are the exception to this and primarily gain energy through breaking chemical bonds.
Danpyr draw energy from a variety of sources, but when young, pregnant or healing prefer to ingest "animal" proteins. In a sense, they are omnivores but on a physical level they are obligate carnivores that have the ability to eat other things. Danpyr that travel off world and especially out of system can have more varied diets or much more restricted ones depending on local flora and fauna.