I dont seem to understand how this is supposed to work.
I have corpses and purple mist outside the wall.
I put a grinder on the corpses. Nothing happens.
The bots cant collect the corpses either.
How do you get them into the machine?

Good point, I probably should have included an explanation on how to play this mod, sorry about that!
I'll take this post and put it in the FAQ after.

How this mod works is it adds 3 new mechanics to the game.

1. When the biter grinder buildings are melee attacked by a biter, if the grinder has space it will kill the biter and pull it as a liquid into the grinder. Once it has enough "biter" fluid, it will activate the recipe and produce biter blood
2. Whenever biters die they release a blood mist that hangs in the air for a bit, this mist can be collected by the humidity condensers and turned into biter blood as well
3. Lastly, if enough biters, spitters, worms or nests die within a chunk a blood aquifer will spawn and can be extracted with a pumpjack

Hopefully that covers the new and unexplained mechanics!
Let me know if you need more details!

I do see the Mist and i have build condensers but their range seems abyssmal?
Can they not reach it from behind the wall?
I would expect about a range of 30 for the tier 1 machine.

The pumpjack makes the most sense but they amount spawned is so low.
Even after 3 hours of multiple larger rampant groups running against the wall
i had 4 patches with about 35k total.
And the manual nature of it makes it an earlygame novelty.
I had wanted to use this mod together with BNW to get some early Oil.

The grinder is nonsense.
I would have to deliberately weaken my defenses to allow enemies to reach the walls
in order to get a handful of extra resources.
A mod like this is almost certainly going to be played with a very high level of difficulty.
Having uncertain defenses when everything outside the wall is red seems like a bad idea.
And the fact that the thing needs to be fueled is crazy inconvenient.

I have now given this another try with the grinder and it does not work,
atleast not for my game.

The smallest biter and spitter larva from rampant are poundig on the machines en mass.
The biter only have 15 hp but almost regenerate faster than the machine damages them.
The spitter take no damage at all, neither do the worms.
There is no mist being created and the grinder never activates its recipe.

Does this whole mechanic only work with the standard enemies?
I am looking at what little of the code i can understand and every single fluidamount and
mist type seems to need explicit input for each enemy.

For time being you might wan to tag this incompatible with rampant.

Oh I see the issue, please see this thread: https://mods.factorio.com/mod/biter-factory/discussion/656da987dade804d850b8b21
My mod currently isn't compatible with rampant.
Meaning that the biter's from the rampant mod don't do anything when they hit the grinder currently.
When I fix this I'll respond on this thread, I'm just not sure when as it will take a lot as there are so many biters in that mod.
But when it's there it will probably be worth it!

I did check to see what might be required for this
but after seeing that rampant generates most of its enemy types with a half automated function i gave up.

Currently im trying with https://mods.factorio.com/mod/Biomass
and after a few hours it makes alot more sense than your variant of biter resources.