Honestly, at first it was nothing but a peace gesture.

Michael was just trying to be helpful. His troops needed some training, preferably in a arena where they'd be stretched a little, and everybody in Heaven knows that Blandine is perpetually overworked. It seemed reasonable for him to suggest that the Archangel of Dreams allow a small number of Servitors of War to do a rotation through the Vale. Potentially useful, too: if she ever needed backup, Blandine would have at least some members of the rest of the Host that understood the terrain.

Blandine was skeptical. Not precisely at the idea, but about whether Michael's Servitors would be able to function properly in the Marches unsupervised. On the other hand, everyone was being civilized about the whole thing, so Blandine decided to compromise a little. Michael could deploy forces there … as long as they had prior ethereal experience. Former Servitors of Dreams, those gifted with the Dream Walking Attunement, a reasonably high levels in the Songs of Dreams, or something similar. Everybody else would have to wait until the experiment was over. Michael did grumble a little, but it was about what he was asking for, anyway, so he didn't complain too much. At about this time David, thinking that the basic idea was sound, signed on as well.

Please bear in mind that at this point, nobody was looking to screw over anyone else.

Michael and David got together and started making up lists of qualified personnel… and got pleasantly surprised. They had quite a few more than anyone would think (especially Blandine). Lots and lots more. It was amazing how, over the millennia, so many angels had switched jobs, spent some time on the pickets or in the Crusade, done the Word of Dreams a favor, or even Redeemed from Beleth's ranks. Of course, relatively speaking, only a relatively small percentage of their organizations qualified: however, a small percentage of a very large pool of celestials adds up fast. They had broken down their review by Choir before they started, and reviewing the lists of Malakim alone took weeks.

Finding out that they had over ninety thousand qualified Malakim alone was still quite shocking, though. This was completely, utterly, unexpected. It was practically an embarrassment of riches: they had altogether too many angels for mere raids and reconnaissance missions…

David and Michael both began to smile. Very, very nasty smiles.

Blandine is going to be very infuriated soon, and for good reason. David and Michael have cooked up a plan between the two of them: Michael sends in his Malakim to the Vale en masse, swarming over every demon they see. Five to one odds sound about right. Most Servitors of Nightmares tend to work alone, so overwhelming them with superior numbers should work in the beginning. Of course, cutting them off from Beleth's Tower would be desirable, but Michael can use support troops (read: every other Choir), calling them in to handle that for just long enough for Beleth's Servitors to clump together. That's when David's Malakim show up, screaming and snarling, bolstering Michael's raiders. Granted, they can't actually hit first, but that's rarely an issue in a melee battle after the first nanosecond. Hit hard, smash formations, take out as many of the big boys as possible.

Of course, David and Michael will be in the thick of things themselves, so they'll know the best time to order everybody back. They're raiding, not starting the Final War, so accomplishing strategic surprise and then withdrawing is neither permitting evil to live when it's their choice or retreating from a fight. Superiors can rationalize a lot of things. From their point of view, they've come up with a plan that could decimate Beleth's Servitors and capture a large part of the Vale

Of course, from Blandine's they've just condemned her organization to a nasty war to the knife that would virtually force her to accept help from two Archangels she personally can't stand, which is one reason why they haven't kept her up to date. The effect of all of this on the corporeal plane isn't going to be pretty, either: a lot of people are going to wake up scared out of their wits (many quite literally), or not wake up at all.

Any angel that stumbles across this is going to realize that this entire situation is going to have messy permutations all around. About the only thing that could shut it down before it starts would be getting either Blandine's or Laurence's personal attention, which may be hard if they're not Servitors of Dreams or the Sword, don't know any, or don't know the location of appropriate Tethers. Dealing with David or Michael afterwards may also be a chore (read: painful and excruciating), unless the PCs can cover their tracks well enough.

Oh, and how much time do they have before millions of dreams are shrouded by black wings?

It depends. What time is it?

Pleasant dreams.