The Psychopath Mother

They will use the children as weapons regardless of the consequences for them.
Children are "remote controls" for a psychopathic-parent, she can use these at will to set off some drama for you and them, she can push the button and enjoy the show. Any clever psychopath will know her children (or you) well enough to know which buttons to push. 

Here you can make it more difficult for her if - in time (a long time) - if she is excluded from the kids' activities (which she couldn't care less about anyway) as much as possible and gets more clueless about their life.

They do not love their children, but will demand love in return.
And even when the children do adore their psychopathic-mother it will still not be enough, it never is. It will not be enough to appease her, not enough to trust the children and not enough to be there for them. On the other hand, any lack of complete adoration from the children will give her the 'right' to retaliate.

They will never co-parent with you, they will counter-parent.
In other words, she will make it her top priority to undo your parenting efforts (and most of all your love) with the children and make you fail with her as a parent. Not only is this a horribly tough battle for the caring parent (and a very long one), it is a nice 'hobby' for the psychopathic-parent, it is thrilling to see how (sometimes with very little effort) she can undo your hard work and make you suffer.  

In later years, if you are still together with the psychopath, she will convince you that you did a terrible job as a father and that your children are monsters, drug addicts, you name it.  Outrageous lies that you will actually believe without an iota of proof - just her lying words will convince you by then.  She wears on you like child labor wears the mother down to the point of birth when, finally, then, she doesn't even feel the ripping of her own flesh.  

You will likely be medicating by then with whatever it is that allows you to quasi' cope , and the more outlandish the lie of the psychopath partner, the quicker you will be to believe her and denounce, then, if in word only, your own children.  The psychopath wife and "mother" grins with approval.  I have seen this in my own family.  My own father who I loved so much and I were her perfect victims, as well as my siblings who served as intermittent victims/accomplices.  

Co-parenting even in a marriage that is together, for a psychopath results the same way.  This is exactly how they behave inside the family with their children and their husband.  It's a kind of Hell at Home.  

I wrote the last three paragraphs.  The first three are a compilation of other writings...