Explain every line, as well as the title.
I am here, I am alive, rapidly decaying, moving all the time,
I am used by politicians, doctors, or even niche artists,
In fiction, I can be custom, achromic, or even mixed with machines,
I need to be fed, pumpkins, kidney beans, or maybe some meat,
I can sadly be hurt, by pointes, tinea, fire, even myself,
When I die, I am given a tomb, rain pouring down on my rest.
What am I?