In answer to your request I have looked into the possibility of indenturing a Dream Demon to your service.
Firstly, I have looked at them as a demonic race. I must tell you, it has given me many nightmares but then you also pay well, Most Gracious Lord, and your recent protections of these past nights have eased my sleep no end.
These creatures are lethal and inspire fear even amongst others of demonkind. They are considered barbaric savages and even no better than animals by the higher ranks. That is not to say these demons are stupid. Far from it, they have an intensely violent and cunning nature able to use many guises to lull others into that false sense of security. However, they are ruled completely by their true Nature, which is wild, predatory and unhampered by any kind of moral framework.
The demons are very social amongst their own (they have to be for no other with any sense will go near them) and they divide themselves into loose groupings of close family relatives even though they are solitary when hunting. They have intense familial ties and loyalty. Their courtship rituals are arduous and, of course, violent in both physical and spiritual senses. They mate once and that's for life, and they will bear only one childing during that time. Demon childlings are prized highly and mostly well looked after for obvious reasons. I say mostly with good cause. It frequently happens that one or other parent may attack their childling out of frustration which is almost always fatal, yet they contain no natural viciousness, simply an inability to restrain themselves and will often go on a murderous rampage through the Dream Realm in their grief afterwards, for such violence is an integral part of these creatures.
Needless to say, the childing mortality rate is high and their numbers do not grow markedly but remain constant.
For one to attempt to capture, tame and indenture a mature adult is beyond the bounds of reason for it would not succeed. (There are no old Dream Demons for the others kill the oldster at the first signs of frailty.)
I propose capturing rather than summoning, for summoning would be entirely too dangerous and you do not want to give this sort any advantage over you. You would therefore need a young childing and I would recommend one born in into captivity. You would need the knowledge and will to restrain it vigorously both by mundane and arcane means. Such training will no doubt be a long term project, involving the repeated infliction of pain and terror, as part of the breaking process as this is the only means by which you will wear even a childling down. Eventually through your determination and will by the repetition of these techniques, it will break.
As you can see this should not be contemplated by anyone who cannot afford the outlay of time and effort and manpower that spans (years equivalent for Courts) rather than (months equivalent for Courts) but you would end up with a fully indentured Dream Demon, which will greatly enhance your advantage over your enemies.
NOTE: It is also my observation that should you wish to proceed you should capture a mature demon of this type as one parent and breed it with either another lesser demon or even perhaps one of full Chaos Heritage (though the latter comes with definite problems and I'd find it hard to assign anyone to such an arduous and possibly fatal role).
After the childing is born, I would terminate the demon parent forthwith and also remove the other parent, thus completely severing the intense familial bonds that could interfere with the breaking process and ultimately allowing those bonds to form into the level of loyalty towards you. Even so I rate this with a less than thirty percent chance of success.
I should also point out that the childing's progress should be watched carefully and all sexual feelings should be blocked before they begin, as even with a successful breaking and indenture, such intense physical and mental stresses on their physiology could bring about a regression to their true Nature, which I for one, would not care to witness.
[Note on the Author of this letter: [Ambrosius was a well-known information merchant who gathered all sorts of information for any House that paid well enough. It was unfortunate that after his death many unwanted secrets fell into the public arena. However, as there were embarassing and scandalous secrets from just about every major House, no-one claimed the advantage. His death was put down to natural causes when he suffered heart failure of both his hearts during a natual sleep cycle.]