Looking like an excellent and characterful start.
Comments:
- Hellblades, stats and points costs should probably be those found in the playtest stats pinned in this sub-forum. Same for Helltalons.
- The Daemontitan rule allows you to summon D3 Daemons via
teleport once per game. Are these Daemons part of a seperate formation? Do they stay around for the rest of the battle or disappear at the end of the turn like the Daemons in the Black Legion army list?
- Devestation class cruiser is probably too cheap by 25/50pts
- Plaguemaw cannon is a bit better than a Free weapon system, possibly should be +15pts if you're game for non-25pt divisions.
- Blight Drone Hive, possibly not a good idea to have Blight Drones and Blight Drone Hives doing two entirely seperate things in the list. I like the concept though.
- Terminus Howitzer could easily go to +50pts and still be very worthwhile.
- Morbus Cannon does not specify what kind of attack it is. BP? Couldn't find a points cost for the Morbus Cannon.
- Blight Missile, needs to state whether created units are all part of one new formation, or several new formations. Can it affect Necrons? Tyranids? Possibly best to leave this Special Rule out of things for that reason. Could have the weapon simply create 7 Zombie units (Nurgle's number) in the impact crater after the shot has been fired.
- Blight Drones, I believe the rumoured weapon set for the Blight Drone is very different to your stats.
- Ah I see that summoned Daemons are to form a new formation, but only through inference due to the 'Daemontitans and the Summoning Pool' rule. That rule belongs at the begining of the document, not halfway though, as it is an actual rule, not a clarification.
- Due to the scarcity of Daemontitans, having only D3 summon points per Daemontitan means you'll likely only get a couple of Daemons, total, into the game. Not very EPIC.

Overall the list has some brilliant ideas and I'm impressed by the ammount of cool background text you've written for it already.