Editing Warhammer 40,000/9th Edition Tactics/Death Guard (section)

===Contagion Discipline===

#'''Miasma of Pestilence''' - Warp Charge 6 Blessing. Select a visible friendly {{W40kKeyword|DEATH GUARD}} unit within 18". Any attack that targets that unit is at -1 to hit. 
#*Note that overwatch hit rolls cannot be modified in any way, so you can't become immune to Tau shenanigans. Unfortunately, this doesn't make plasma explode on 2s anymore, and to-hit modifiers don't stack beyond -1, but sticking it on a squad of Deathshroud or Poxwalkers or Mortarion will still make them a pain to kill.
#'''Gift of Contagion''' - Warp Charge 5 Malediction. Select a visible enemy unit within 18" and debuff them with -1S, stacking -1A as well if you roll an 8+ on the psychic test.
#*This power is bad, there's no really good way to sugarcoat that - Dark Angels (Aversion), Deathwatch (Neural Void), and Thousand Sons (Dysmanifestation) are all examples of other Space Marines with access to this power but better, because -1S is such an incredibly weak effect.  Unless your psyker can re-roll the cast (e.g. from the Sevenfold Blessings strat the Wretched have), you can just assume you won't manage the -1A rider (which goes off only  27.78% of the time).  To give you an example of how weak -1S is, if you try to protect T5 plague marines from a mixed squad of loyalist Marines attacking with Thunder Hammers and Chainswords, -1S will do ''absolutely nothing'' - S4->S3 has no impact on T5, and neither does T7 (your modifier applies after multiplication for the same reason a +1 modifier makes a Thunder Hammer S9 in 9E, not S10).  The power is incredibly reliable in terms of the base effect, mind - you'll manage to debuff the target's Strength a full 5/6 (83.33%) of the time - it's just that you have to pick your powers before you know what you'll be fighting, and a ''lot'' of the time -1S is useless.  
#*Unless you chose a particularly useless company contagion - looking at you, Chosen Sons - odds are incredibly good you're better off with Gift of Plagues, in terms of using a psychic power to debuff the enemy.  If nothing else, Nurgle's Gift for -1T is a good deal more useful as a debuff than -1S. 
#'''Plague Wind''' - Warp Charge 6 Witchfire. Select an enemy unit within 18" and roll a die for each model in the unit; 6s cause mortal wounds. If you scored a 9+ on the manifest check, you instead deal a MW on a 5+. 
#*Effectively, this won't ever do much, but as it is one of the very, ''very'' few things left that scale with target unit size; you should take this if you are seeing huge tarpits on the other side of the table. And hey, what other Warp Charge 6 power can kill 8 Conscripts (assuming a 48-50 man blob) on average?
#*WC6 means the expected mw per model is 1/6 after accounting for the casting check, which means the power beats Smite against any unit of size 11+.
#'''Putrescent Vitality'''- Warp Charge 7 Blessing. A visible friendly {{W40kKeyword|DEATH GUARD INFANTRY}} unit gains +1S and +1T. 
#*Like your other buff spells, this one affects units and not models, so use it on those Poxwalkers and make them undying. (Particularly useless with Typhus in that his Poxwalkers are already S4, and thanks to Nurgle's Gift going up to S5 isn't a big deal.)
#'''Curse of the Leper'''- Warp Charge 6 Witchfire. If manifested, roll 7d6. The closest enemy unit within 18" takes a mortal wound for each roll that exceeds its toughness characteristic. 
#*It might not have the potential to cause more mortal wounds than Plague Wind (and won't work at all on units with T6 or higher for obvious reasons), but it's more reliable against units with lower toughness. Like, just as an arbitrary example, the ones that have been debuffed by your contagion.  Generally speaking, only better than ''Smite'' against T3 or below, which includes space marines if you manage to get them in range of Nurgle's Gift.  As a corollary, excellent synergy with Gift of Plagues (or if you're playing Terminus Est, Gift of Infection). 
#'''Gift of Plagues''' - Warp Charge 6 Blessing. "So wtf is this spell and where's my Blades of Putrefaction?" You ask. Sadly, that power is done for, may it rest in peace. Instead, this power boosts the range of any contagion of a {{W40kKeyword|DEATH GUARD}} unit within 18" by 6" (maxing out at 12"). Considering you can use it on Mortarion for a 12" bubble of whatever extra contagion you gave him, or you can combo it with Flash Outbreak to get a forward-punching unit to spread your warlord's contagion, this seems really strong if played correctly. Halving all movement or shutting down re-rolls to hit/wound with an extra 6" is a game-changer.