[LDiCesare]

The Nexus is enough to make Ermor more of a threat long term than Agartha in my opinion. It's not a spell you want to cast if you don't expect everyone to attack you, ever. Why should I join forces with Ermor to attack Agartha now? I'd have to build items for my SC's. That would bring gems to Ermor. I might want to cast spells. That would strengthen Ermor. Should I defeat Agartha with Ermor and Sauromatia's help, who would have a gem income of twice or thrice my own?
I was to attack Agartha on next turn, and this was public knowledge. But the Nexus makes it a bad idea. Should we defeat Agartha, Ermor would have twice as much income as I, so the game would be won by them. No point. Taking out the Nexus is top priority over everything else, sorry.
If you want TC to attack Agartha now, dispel your own global or suicide its caster.