Opacity Issues

Hi, I've recently downloaded Stager and I've been trying to render some textures made is Designer and here is the problem :

I've made 2 cylinders (merged) with different material in Designer, they're the same just one have a very smaller radius.

Then I've made texture with opacity and a lot of displacement but the thing is the part that should not be visible still have an impact on the final render. 

As we can see on the first screen the bigger cylinder with height get a bit thinner at some point than the other one but this last one have opacity map that makes him invisible.

Still, as we can see on second screen the absobtion color is impacted aswell as the base color (the dragon suddenly lose his color).

Maybe it's not a bug and I'm doing something bad ? If it's the case I'd be glad if someone explain me.