Actually many people consider the Order to be the most thematically appropriate religion for the Calabim. The two best religions for the Calabim are the Ashen veil and the Order IMO.
If you want Ashen Veil, it will be for the Sacrifice the Weak civic. This civic enables all population to consume only 1 food per turn instead of 2. This can get you some *huge* cities, you're basically doubleing your population capacity provided by food, although you will still need happiness resources/religions etc to keep the population growing. StW would also allow you to convert some of your now unneeded fams into cottages to help get ahead with technology.
But....
The technology that gets you Sacrifice the Weak also summons Hyborem into the world. This is worse then it sounds, for the Calabim. When hyborem is summoned hell terrain starts to spread, this destroys useful floodplains and resources and (iirc) has a lower food yield then normal terrain.
A viable strategy might be to run AV to get some huge cities, then feed on about half of your population with vampires and convert to the Order before hell terrain reaches you. Order will turn you good which will give you the advantage of being completely rotected from hell terrain spread.