In a world with real monsters, a desperate griffin and his team fight through the expanding zombie horde to deliver an immune human to their superiors.

For me, I think the problem is that there are too many good ideas here.

For instance, I'm counting 5 players:

real monsters, a,griffin (a monster), the team (of monsters), zombies (also a type of monster?), an immune human (type of human, i.e. the immune kind), superiors (monsters).

It might be easier juggling so many characters if it was a real world, because you could rely on the reader making assumptions. Here it gets overwhelming. I'd consider dropping the number to, say, 3. Sure, you loose some of the detail, but too much detail seems to be the problem.

"In a world" sounds a little too Don LaFontaine.

Its a fun story. I like seeing all the updates.

How about A desperate griffin and his team of monsters must fight through a horde of zombies to capture the only thing that will return his family's honor, an immune human.?

From what you said above, it seems like loyalty and honor is what really matters to the griffin. Finding and retrieving an immune human is just a tool to get back what was lost. Just throwing out ideas.

Yes, Monsters eat humans (without human blood they weaken and eventually die), Zombie plague happens, Monster's risk exposing themselves to stop the spread of the infection. Zombie blood lacks the proprieties that sustain the Monsters so they can't eat them. It's actually the same reason Zombies eat humans.. for the same property.. the addiction is just so extreme that it overrides all other brain function including survival instinct. In the end we learn that the plague came from monster blood that has been experimented on.