As said above you would need to have a CAD for the army that wants the LOW. Slighty easier for you than going impy guard allies is renegades and heretics from either Imperial Armour 13 or the newer Seige of Vraks book. These are simalar to guard, but are chaos versions. To fill your min requirement of a CAD it would be a command squad with covern of nurgle and 2 units of zombies costing you somethong like 120pts total. Though check out how cheep griffons are and how badarse they are... Espesially in purge formations.
Each has a 12-24" S6 Ap4 ordnance, barrage, large blast, pinning shot, and can reroll scatters. Also if purge that blast remains till your next turn. This leaves behind dangerous terrain... this means that anyone you hit on there will have to take a test as soon as they "enter, leave or move though" dangerous terrain. But you only take a max of 1 a turn. But either way roll a d6 and on a 1 you take a wound with armour / invuln saves allowed but not cover. Also it classes as difficult well so roll 2d6 move and pick the highest. This can easy tarpit larger squads. Vehicles though they take a hull point and immobilise, what is great for crashing skimmers.
Oh and add to this that gun is mounted on 12-10-10 3hp and has a heavy bolter, though is only BS2. Though what can you expect for 35pts!
So now you have that in the army they have access to tanks such as the Malcador, Malcador Defender, Minotaur and Renegade Baneblade.
