Diplomacy in H5 -- how does it work?

[Gaidal Cain]

You know, earlier you got -1 morale if you had undead in your army, besides the -1 you got from having necropolis troops.

[DaemianLucifer]

Oh that one.I never mixed with necro.Didnt find the need.Skeleton archers are all you need.

[Asjo]

It was kind of overpowered earlier, which I liked. When you had a big army, it just kept getting bigger, and I was able to feed three or four other heroes with the units that my main hero with diplomacy picked up. I really liked that, even if it was obviously too easy if you got to that point. If you had left a lot of creatures on the map, you could pick up the craziest additions to your army that would give you a clear advantage against the opponent. Picking up 150 liches will quickly make your army too powerful

Diplomacy has always been my favourite skill, and I like that in Heroes V is seems that the entire neutral stack joins you, instead of a specific amount of experience points worth of creatures based on your hero level.