[Cohen]

I talk for MP experience.

Personally I prefer however Watchtower. Even if I pump out less HeavyInf.
First try with a combatant pretender, Caeseus, like the Ghost King that now as it is, it's like a jolly because he could do almost anything.

You could exploit Death til 3, that Abysya won't lost the gold income nor the supplies. But the population will die however.
Pick always magic-3. It's the lone way to have a decent research, considering your bloodhunters and researchers are capitol only (I mean those cost-effective, even a 200 gold costy ant.salamander can research).
For productivity, it's not that useful, soon the heavy infantry get useless AND considering that a rout in any battle == them all dead, AND the time you need to replace an army of them, AND a huge amount of time to bring them in an attack position, AND if in early expansion you get your way closed by another nation, or by a sudden appearing of 4 heavy cavalry province all neighbouring the new aquired province and you've to waste a turn to get back, you'll discover the Abysya Infantry is very poor for their cost. And with their low morale they'll flee very easily. You can consider Productivity only if you want extra gold. Your pretender should be the way you conquer indies, Abysya really lacks of a capable army.

About Air Queens, forget them. To have that research and air income you should find a lot of sages, or indep mages. Even if they're awesome.

I usually go at least blood-3 before any construction, and even blood-5 if my pretender is capable of binding Ice Devils. The lone Abysya benefit is that her blood hunters start with 2 blood, so if there's the devil race with mictlan you can forgo the sanguine douzing rods. But usually expect Abysya get outmatched in blood by Mictlan, default Jotunheim and Black Forest Ulm.
You need however blood 3, if someone go at war with you and you can't hold him at bay with pretender and heavy infantry (thing very very easy), demonbred can summon single devil, and warlocks can summon fiends of darkness.
They're good raiders if led by a Demonbred, they can't hide but they fly.

Fire Magic doesn't count a lot. Abysya has no real battle mages. With low precision, to be useful you've to send an entire battery of Anthemats in battle, and when you go to the fight the enemy could easily make a ring of fire for his most precious leaders.
Communion? Well Warlocks perhaps in communnion could do something, HEY but they're your lone researchers and blood hunters, unless you're desperate do you really send them into the battle?

However Abysya isn't one of the top five nations, IF there's another blood nation in. If in the game perhaps there'rent the 3 above, oh well, it's quite different.
Even in my opinion is one of the weaker nations.