Religions deserve serious consideration in every Fall From Heaven game, and even more so with a leader and civ that can switch between them at will and derive unique benefits from priest/disciple units.
It's not unusual for a Malakim empire to gather about 4 or 5 religions and use them all at some point. Let's go through all of them (evil to good) and talk about how they can be useful for my game.
I certainly have no plans to summon Hyborem, but Ashen Veil could be useful in a city or two of mine. If I want a quick source of collateral damage I could spread AV to one city, pop my worldspell for a ritualist per city to cause some pain with ring of flames.
Lightbringers with a load of starting experience can also pull off a neat trick with AV. They can upgrade through savant straight to mages. They don't get arcane promos along the way but with a few of the same mana source can start with useful spells.
Can't stay in it too long as the altar can't be built by evil civs, but I'll probably make a pit stop for AV in a city.
Don't want to spread it too much. Both to keep the AC down and because it conflicts with other plans...
No unique units that I lust after, I think I'll let the others fight over Gibbon.
If it's ignored for long enough it'd be useful if I could found CoE and build Nox Noctis. Otherwise I'll probably pass.
Cultists can dominate on certain maps, and I have a big shiny button that could create a lot of them out of the ether, but I don't see this map having enough bodies of water to make them particularly devastating. I do think Fanaticism will be in my tech path so might be a detour for some stygian guards is the situation is right for them.
Hemah is great but I'll probably be concentrating elsewhere by the time I could research arcane lore.
Kind of a standard religion to pursue early when you're not on the water or the elves, but it's always kind of underwhelmed me. Heroes are forgettable, won't help pop borders (as I plan to switch away from creative at t75), and the priests aren't anything to write home about. I'll probably go with markets to keep the economy afloat instead of the gold from Kilmorph.
Maybe if I just want the benefits of any religion and it's looking like it'll take a really long time to get to the later ones.
I probably won't found it, as there are elves in the game. Even so, I'll probably adopt it for a while. If I burn some jungle and get some forests in their place, lumbermills may be necessary to garner some production on the almost too green and flat rainforest script. Making those tiles ancient forests would, of course, be a boon.
FoL may also be the religion of choice for popping my worldspell. Priests of Leaves to bloom and also summon tigers to soften stacks or add a happiness to cities with carnivals. Wouldn't mind having about 6 of these guys.
Empyrean seems to fit with the Malakim thematically very well and it would be nice to get some radiant guard or rathas (especially as I didn't choose haste or slow on my adept to swing the mobility in wars in my favor).
Usually would be chosen with the hopes of landing Chalid, but I don't think I'll be headed for him.
The ultimate good religion which I sort of rarely use in most of my games.
I think that's about to change though.
I foresee myself adopting Order after popping my worldspell and staying in it for good.
Priests add +1 holy combat to units with their Bless spell. Order is super easy to spread over an empire as every time it appears in a city you have a 75% chance to spawn an acolyte who can spread it again, rinse, repeat.
The shrine, Code of Junil provides law mana which dovetails nicely with my plans. Law from the shrine plus my palace mana puts me only one mana type away from being able to build the tower of divination (a national wonder oracle). The plan would be to divine the righteousness tech as its expensive, required for a more advanced level of the altar and it unlocks Sphener (an awesome angel hero) and paladins. Sphener, in addition to being a good unit, looks bad ass enough to more than make up for the dopey looking Valin Phanuel.
Fanaticism, which is required for righteousness, also unlocks the mercurian gate. We haven't seen the mercurians yet in these pbems but if I have an outlying city with some good production I'll probably try and build it for a permanent angel ally.
And there you have it. The religions and what I might do with them.