oh it's my pick... let me do some testing and ill post shortly.
some of the nations get recruit any fort sacreds by the way.. but the sacreds are so-so
EDIT - thinking outloud
I thought
Pareldocia was OP ... but lack of good priests and even though their sacreds are tarantulas with glamor and stealth... they dont get web and protection is average... and more expensive than normal tarantula knights.
Considering
Shela - summons are rubbish...(no late game) but
they get a recruit-anywhere SLT earth 3 mage with 25 production bonus.... they also get a 100 mana 2-earth mage.. and a national spell that gives them communion via earth magic.
So potentially just horde tanky troops and earthquake/bladewind spammers.. unfortunately they seem to be 1-trick-pony and worst of all only get a single level 1 priest ;D
There's Qurgya that gets these badass flying knights which is awesome.
Sacreds are so so.... 6/10
They get Sirrush because, why not...
late game any of their capital mages can cast volcanic eruption...
thinking thinking...
Zris is obviously good, but i dont really like their commanders... no good communion slaves.. and their mages being heavily stacked into fire is kinda meh... great sacreds and flying non-demonic heavy-plate demons is gangster.
Raqris looks pretty good.. their infantry is less gimicky than Zris.. drops regeneration for an extra 6 protection which is good... much better offense with the flail... They get full-plate crossbowmen with shields.. which is pretty good but fucking expensive...
Most appealing they have 45 gold sabbath slaves.
...
Caessedigh gets pretty scary assassins...
gift of water-breathing sacred and non-sacred giants that turn into giant spiders... and hydras... hmmm... plenty of thuggable mages aaaaand I think i'm sold... just going to playtest Qurgya vs Caessedigh
EDIT 2 -
Damn this is hard picking between those 2... one gets tons of thugs and out-of-the-box guys who can cast MOAK...
On the other hand, we have huge evo spells.. infinite resources coupled with badass flying heavy infantry
Okay - upon seeing they have "ancient professor of metal" I think I'm sold and I dont even like heavy metal.. just love the theme of these guys and Caessedigh probably stronger and I will regret it but whatever.
Final verdict -
Qurgya, The Passionate Circle