Effective Use of Plague Marines
In previous editions, Plague Marines were tough workhorse units that could hold objectives, crack vehicles, and tie up units in combat without much support while the rest of your army was free to maneuver. However, they didn’t have much killing power. In 8th edition, their role has changed. They’re more fragile, slower, and need more support than before, but in exchange they’ve become much more threatening. Plague Marines are now better used as a scalpel to excise troublesome enemy units while Daemon Engines and Poxwalkers become your hammer and anvil, respectively.
One of the biggest changes to Plague Marines in 8th edition is the expanded set of wargear options available to them. They share a number of new melee plague weapons with the Blightlord Terminators, and frankly I think that’s where those melee weapons belong— on the Terminators. I understand that some people have had a degree of success with large Plague Marine units kitted out for melee combat, but I personally can’t stomach turning an already pricey 19 point model into a 25 point one equipped with a knife and an axe. Much more interesting to me is the possibility of packing 3 18” rapid fire plasma guns into a minimum sized squad, but perhaps the most attractive option of all is the blight launcher. This is a 24” assault 2 plague weapon that synergizes especially well with the Arch-contaminator warlord trait, and which can put out multiple damage without the risk of instantly losing an expensive marine to a bad die roll.
Plague Marines have access to a powerful stratagem, Blight Bombardment, that allows the whole unit to hurl blight grenades at 6”. This would mostly be a novelty if it weren’t for what I believe is the most important support character in the codex, the Biologus Putrifier. The Biologus turns the weedy S3 grenades of the Plague Marines into S4 D2 bombs that produce additional mortal wounds on a wound roll of six. Coupled with Blight Bombardment and Veterans of the Long War, even a small unit of Plague Marines can output a huge amount of damage. Even a single opportunistic grenade thrown with the Biologus’ buff can be threatening to low wound count characters or small squads. Taking Plague Marines without taking a Biologus Putrifier is like taking Poxwalkers without Typhus—you’d better have a very, very good reason.
My preferred approach is to mount a small squad of Plague Marines in a Rhino with a Biologus. Seven marines is about perfect since that’s just large enough to get good value out of Blight Bombardment without tempting a bad emergency disembarkation or failed morale test. I make the Biologus the warlord. He gets the Arch-contaminator warlord trait, allowing the marines to re-roll all their wounds with blight launchers and blight grenades; this paradoxically makes the unit better at assassinating higher toughness targets, since more rerolled wounds mean more chances for mortal wounds.
A Plague Marine unit such as the above will greatly benefit from any other support you can throw at it— a nearby Daemon Prince to grant re-rolls to hit, an allied Sorcerer to Warp Time them near a grenade target, etc. That said, be careful not to tunnel vision on pumping up that squad to the detriment of the rest of the army— Death Guard don’t have the points to be excessive. They should be a useful troubleshooter rather than the be-all, end-all of firepower in your list. Plague Marines are too pricey to be expendable so draw attention away from them with aggressive play from tougher units like Bloat-Drones, allowing your opponent to forget about them until they can strike. It’s important to be opportunistic rather than aggressive with this unit, waiting for an ideal time to spring the payload of grenades on a high value target. Mindful play will allow you to get value far in excess of their admittedly large price tag.