Being a god can not be that bad. We have seen a few and they seem to amuse themselves.
And we also are told that they have very limited ability to affect material reality. We have no reason to presume that they have mortal free will, and the few we see are rather strongly aspected, in terms of having power within a particular sphere of interest or influence.
Cowl could have taken the amount of power he needed for his next undertaking.
Why would you posit that god-tier power in the specific direction of necromancy is useful to the Outsiders' goals, whatever those might be ?
With Cowl it is not about order or chaos on a personal level, it is about reaching goals for the outsiders in a really short term say before the end of the series.
That seems an unwarranted assumption to me. We have, sfaict, as yet no clear idea of Cowl's endgame; nor do we know how long he has been doing this. I would argue that him being Senior Council power level suggests he's been doing whatever he has been doing for a fairly long time, given that the examples we have seem to be wizards of multiple centuries in age.
The power would be useful. It is would bring the end of reality closer. He could not let it go.
And again, you are asserting that the guy is essence of Chaotic. That he has no impulse control whatsoever, no ability to throw over a short-term possibility for a long-term plan that may be more in keeping with his ongoing goals. We have evidence that he has been working with Outsider-related stuff both in GP and in WN, and at least the plausible suggestion that he has been doing so a lot longer. The thought that he would throw that all over to grab particularly at necromantic power makes no sense to me.
Consider instead; Cowl and Mavra are working together. Cowl and Mavra work together in GP towards greater supernatural instability; setting up Lea to get the athame is also setting up Mavra to get Amoracchius. We know from SF that Bianca does not leave her enemies alive, she says so directly to Harry; therefore the whole Rube Goldberg scheme of inviting Harry to the party and kidnapping Susan to torment him is
out of character for her. We do not know all of what is going on there, but we do know Bianca learned dark necromantic-type magic from Mavra, Harry registers this. We do not, technically, know which of them was running the Nightmare, but with the Nightmare as a sock puppet, Harry can be manipulated in a fairly detailed and immediate level all through that book (by his reactions to the Nightmare, to various other Red vampires, to the ghosts Mavra or Bianca torments with the black barbed-wire spell, and by Mavra and Bianca directly). Which succeeds in removing Amoracchius' protection, and which succeeds in pushing Harry and Bianca to a final confrontation which starts a war between the White Council and the Red Court that benefits neither of them.
So if we look at DB from the perspective that Cowl and Mavra are working together, things become clearer. Bony Tony is set up to find the Word. Mavra manipulates Harry into taking out the competition. (The photographs she takes of Murphy in BR to blackmail him in DB are fairly convincing proof that this is a deliberate set-up, to me.) Mavra wants the Word under control because, according to Harry in their confrontation at the end of DB, the Word contains instructions on how to use necromancy against the Black Court.
And, when Harry and Butters are talking in DB about the circumstances that made Chicago a possible place to have the Darkhallow, one of the things cited as contributing to that is the turbulence in the border between the NN and the real world there. Which is caused, in DB, by the ghosts tormented by black magic. So Mavra has actively contributed to making Chicago a possible Darkhallow site from several years earlier.
I find it easier to buy this set of cross-connections as competent people planning together than as people with poor impulse control blundering around like Keystone Kops and jumping from one plan to another whenever something shiny shows up. Particularly when the end result keeps being that people who jump for immediate gratification get killed in ways that benefit people who don't.
