Attacks - They will wander around for a while and then swing their big casket around twice and then plant it in the ground. They will then summon 2 Hells (usually Prides) which will appear if you don't kill the Greed before the mist vanishes.
Dangers - If you get hit by their casket then it will cause a fair bit of damage but by far their biggest danger is their ability to summon 2 other Hells. On DMD mode these guys are a total nightmare, kill them first in a mixed group without exception. They also have a ton of hit points, more than any other lesser Hell which means that if there's 2 in the room, at least one of them will almost always be able to summon some Hells before you can stop them.
Weaknesses ' - They're not weak to any weapons but they are incredibly slow. In the time when they're wandering around they will not attack, use this opportunity to lay in as much damage as you can. On the easier modes you can easily kill them in one attempt.
DMD Notes - If these guys DT then you are in big trouble. There's only ever 2 of these guys at most so always take them out first, regardless of who else is in the room. You'll end up with a room full of Devil Triggered enemies, but that is far better than these guys going into DT and spewing out enemies until you are finally able to take down their massive health bar.