Epidemus and allies

[Gorefather]

Ok, so I finally bit the bullet and decided to get some allies for my chaos marines. Epidemus was recommended due to his ability to buff surrounding nurgle units (my current army being death guard). Now Epidemus gets bigger buffs the more kills the army gets from daemons of nurgle. Here's my question- does this include unts with the daemin and nurgle rules from the csm codex? Could nurgle obliterators or warp talons (lol) contribute to the tally? Or is it only models from the daemons codex?

[Nabterayl]

As the codex says, it's any model who are Daemons of Nurgle. There are a few such models in the CSM codex, such as Nurglite obliterators or Nurglite warp talons, as you've identified.

[Gorefather]

Cool. A few plasma cannons should help rack up those kills nice and quick, cheers

[Nabterayl]

Plasma cannons ... of Nurgle!

[Charon]

As the codex says, it's any model who are Daemons of Nurgle. There are a few such models in the CSM codex, such as Nurglite obliterators or Nurglite warp talons, as you've identified.

Both are no daemons of nurgle just models with the daemon rule and a mark of nurgle.
The daemon prince is a daemon of nurgle (different special rule than the mark of nurgle).

[Nabterayl]

Both are no daemons of nurgle just models with the daemon rule and a mark of nurgle.
The daemon prince is a daemon of nurgle (different special rule than the mark of nurgle).
My bad, I had forgotten which CSM daemon models had which rules. Charon's quite right that the Daemon and Mark of Nurgle rules are not enough - you have to literally have a rule that says "Daemon of Nurgle."

[Mad Cat]

Scabiathrax, the forgeworld 777 point megadaemon does have the "Daemon of Nurgle" from the chaos daemon codex if you want to be truly evil in larger games.