Chapter 12 (Elementals) introduced T4 and needed T4 for Chapter needs.
Chapter 13 (Amuni) introduces T5 and Chapter 14 (Constructs) T6, so both exclusively need those, respectively?
Chapters 15 & 16 (Elvenar and Dwarves&Fairies) need all 3, T4, T5 and T6, yes?
The Spire asks T4 starting in Amuni (Chapter 13).
What about map negotiations? Is there a T4 ring analogous to the Orc ring?
Tourneys?
I'm waiting on Mana to complete Elemental's Ancient Wonders and am trying to plan my Amuni city, and trying to decide if/how many Platinum and supporting Marble to retain (vs. Teleport) while building up Inks and supporting Crystals. It almost sounds like I only have to plan for Spire needs and so can cut back one Platinum/Marble.