The Triumph of tides must scale badly, or something. I just crunched numbers in my chapter 7 city. If I set it on supplies this little beauty is worth over 70 squares! Workshops/Residences/Culture.
Also just at a glance its per square production of mana and seeds looks solid, better than an FM. Anyone picking it up b4 haflings could keep it un-upgraded if they need mana more than seeds.
I cater so I did not look at the troops.
Mana wise it's mediocre, especially for anyone who's got some of the previous event mana buildings. (ie: Mana Hut, Lave Egg, etc...)
Troops wise it's slightly better to decently better than a VV available via crafting, but again, the usefulness is gimped because Heavy Melee in general sucks. (...only Light Melee is worse!
)
Seeds is where it's at, since overall seed production is much harder to come by en mass, as IIRC, only the Pond of Autumn is a genuinely excellent option... Festival Merchants are good, but size becomes an issue due to them being 4x3's and their production is well behind this new building.
Overall though as pointed out above, it's a crappy 'Grand Prize', since it only gives 1 production at a time, making it really feel more like a 'limited edition' daily prize.
It should honestly give 2 of the optional productions, or else have 1/4 become a perma feature, even if that resource takes a bit of a nerf in doing so.