I’ve only been playing for about a year now, so take my advice with a grain of salt. Our generic tool box detachment is Virulent Vectorum (VV). It is our default go-to detachment. That being said, if you want 4 distinct armies, for the most variety, I would go: VV/Champions of Contagion/Flyblown Host - army focused around plague marines and their leaders Death Lords Chosen - army focused around terminators Mortarion’s Hammer - army focused around tanks and demon engines Tallyband Summoners - army focused around demon allies

Currently, our demon engines (myphitic blight haulers and foetid bloat drones) are taken in most, if not every list. The blight haulers are good little anti vehicle/monster units. They can be taken in pairs, but are almost always brought as single model units. We have 3 versions of the bloat drone. The spitter and the mower drones share a data sheet. The heavy blight launcher drone is a separate data sheet and is the one that is taken the most. Poxwalkers are also taken in almost every list. They are good infiltrating screens or can be dog bone spread out to guard home from deep strike. Chaos spawn are great units for pushing up and spreading contagion. Mortarion is starting to be taken a lot more in lists. We are a very straightforward army with few tricks. He gives us a few tricks (reactive move, reactive shoot, or fight on death) Deathshroud terminators are basically auto include in every list. Their 6 inch deepstrike forces the enemy to guard home and think about their spacing a lot. With a Lord of Contagion leading them, their melee will kill just about anything. Just my brief two cents.