Reecius posted this really good article recently: http://www.frontlinegaming.org/2014/10/16/tyranids-tactics-the-trapdoor-spider/
While it is a Tyranid article I find it is still applicable to daemons. The general tactics for a trapdoor spider list is to wait and lure your opponent near to your lair, then beat the ever-living shit out of them and drag the rest of the corpse into your lair. The tyranid version consists of lots of 2+ cover, something a nurgle daemon can do easily. So this is my version of a trapdoor spider list:
daemon prince of nurgle
wings
armour
x2 greater rewards
mastery 3
daemon prince of nurgle
wings
armour
greater reward
mastery 3
daemon prince of nurgle
wings
armour
greater reward
mastery 3
x4:
herald of nurgle
mastery 2
x4:
x10 plague bearers
Aegis defense line
1755
Heralds roll on Malefic daemonology and try to get cursed earth and summoning. Princes roll once on Malefic (twice if you get cursed earth) and twice on biomancy. The plan is to get summoning on everything (princes summoning is very effective due to their speed). The Aegis creates your lair, and anything behind it will have a 2+ cover straight off the bat. 17 mastery levels will let you cast what you want when you want. What you do is sit back with everything (including the princes, they are your counter sucker punch) and summon plague bearers just outside your lair (like spinning a web) to lure your opponent toward you. When they get close enough, jump out with the princes to kill the close stuff then run back into your lair. Keep doing this until near the end of the game then jump your prince(s) out to the opponents board edge to get linebreaker. I have found this list to be incredibly effective. The daemon princes give you long reach and lightning fast response. I aim to summon a unit a turn, so you should have about 60 extra plague bearers through the game, which can be used as midfield objective grabbers, meat shields, and support.
Until then,
Cheers.
