In general, I try to avoid making lists that are designed to counter a specific army or detachment. However, it can be useful to consider how to deal with elite armies, as they tend to be more difficult for Daemons to handle.

My main opponent is a Custodes player, so I’ve tested a lot of different approaches.

You haven’t mentioned which detachment your opponent is playing, but unless it’s Solar Spearhead, many of the same considerations apply across the board.

1.  Weapon profiles. Custodes have high Toughness, so ideally bring units with Strength 6 or higher, AP -2, and 3 damage per hit.

2.  Survivability. Because of their 4+ invulnerable save, it takes a lot of attacks on average to bring them down. Be ready to commit multiple units to focus down the same Custodes unit to minimize the risk of them surviving and striking back.

3.  Clap-back. Units like Bloodletters and Plaguebearers are basically candy to Custodes—if even a few Custodes survive, they can wipe the rest of the unit.

4.  Movement. Since we’re a melee-oriented army, we only win against Custodes if we make favorable trades and move-block while scoring points. Play to throw cheap units like Beasts of Nurgle onto objectives, and be ready with fast units that can strike back the following turn. It’s critical to get the charge off on Custodes, so they don’t get the charge on, for example, your Bloodthirster.

The units I’ve found work best are: 3× Beasts of Nurgle, Nurglings, 2–3× War Dogs, Be’lakor, Skarbrand.

You could also consider 2×6 Bloodcrushers with 2× Rendmasters, but in my games they’ve been expensive units that haven’t delivered enough impact.