[calmon]

I would never play this game with Arcane Nexus in the spell list. In my experience you get around ~200 astral gems in a normal full game. So count 500-600 in a big one like this. You would have enough gems to recast it for 999 in the turn after you cast it.

I can second micah, the global shouldn't be in effect in the turn cast (from manual) but up to date it works in same turn.

Utterdark on the other side isn't a real problem. 90% of the nations are affected and so nobody from them got a real advantage.
The 10% which got some advantages from utterdark will be in trouble very soon. Remember there are dozen of nation which can spend for a dispel.