I played another game to test the Esus-mechanics out, lasted a bit longer this time.
When I read this thread I was a bit sceptical of the changes to Gibbon, felt like a bit of a nerf but while testing they fit very well with the overall changes.
The happy-bonuses feel very welcome. I did not do any numbercrunching, but the general feel was that it was possible to steer up the kind of religion-boosted ecoonomy I usually do. No Guardian of Nature perhaps, but considering the synergies with your other mechanics they are very interesting changes overall.
Moving Nightwatch to Deception felt like a very good change gameplay-wise, even though the use of bows outisde of the archery-line felt a bit uncomfrtoable to my lore-minded head. But maybe that is not unique. One of the problems with Esus was always that its benefits were so spread out across the tech tree, Nightwatch at Bowyers (seldom worth the effort), Shadows at the end of the economic techs and Shadowriders so far off I have never even built them.
The promotions granted by a high crime-rate eluded me though. I found a ranger with some elemental or magic resistance once, but that was about it. Since there is no way to monitor crime rates (I think?) this makes it a bit hard to test, but the overall feel was that the impact was so small it was negligeabel. EDIT: I also got a Nyxkin with Hidden Nationality.
And finally, the hidden nationality-aspect. After having built the Ratcatcher's Guild I really felt like the stalky slayers the Svartalfar are supposed to be, my woodlands, an important passageway for many a civ, were safe to noone (and xp rolled in to my troops

). However, Mask as dependent on unit religion is a bit of a wasted ability, CoE as a unit religion is so random and so rare it is impossible to build any religion-based strategies on it.
I understand now why you thought making Mask simply require CoE as State Religion felt a bit cheap, I think wonder/building-dependence is the place to go. Perhaps a wonder /building that allows Recon units present in the city to cast Mask, or one that hands out unit-religion for a fee (though I think that is hard ot code), or simply give Mask/CoE as unit religion to all units produced in the Ratcatchers' City. This would be enough for my playstyle, though I play in small maps with small empires.
Another "cheap" change I myself use from time to is however to let Nightwatch upgrade to the recon line, which works even better now with Nightwatch on Deception, though this might have some promotion-balance issues, I have not really thought/played it through with the attempt to max its benefits out.
Council of Esus has however turned into a viable alternative for more than just the lore and feel of it. The ability to control the hidden nationality promotion with Ratcatcher's, the boosts to happines and indirectly to the economy with a certain set of buildings that also caters the player to a certain economic/civic playstyle suited to the religion lore-wise (this was my feel atleast, played around with consumption, specialists and not-a-100%-sciencerate), cities filled with crime and forests filled with stalking Assassins - a Council of Esus based Svartalfar Empire has turned into quite what I thought it would be.
Great job!
