It appears that this event does not have any mana generating buildings. However, there are several that produce powerful troops (temporarily). And there are a few combo structures that produce population and culture. Please see the following link from CrazyWizard:
http://crazywizard.info/en/event_march_of_the_herds_2017_rewards.html
Thanks for the link, Cwgiii ( and thanks to CrazyWizard too ).
On the plus side, I do like the farmy, rural look of many of these buildings.
On the downside, a building with an effect that lasts only 5 days after placement is hardly worth the trouble to acquire.
The other bulidings seem to be a slight improvement on the standard culture or culture/population bonus, which is fine....but makes almost no practical difference in the game itself, as far as I can see.
I don't know why the devs. won't spare a few crumbs off their table for the poor starving players who are barely hanging-on when it comes to city space, mana production, guest-goods production ....and the various other genuinely difficult aspects of the game.