Research is the progression system that unlocks new buildings and repeatable global bonuses. Research is performed globally for your kingdom and costs Science, so a completed research applies across all of your villages. Researches are organised into tiers (1 through 8), and almost every research has a prerequisite that must be completed first.
Overview
Each research has four defining properties:
Tier: the research tier, from 1 to 8. Higher tiers cost more Science.
Building village tier: the minimum village tier required to construct the unlocked building. The research itself is global and is not gated by village tier. Tier 8 researches unlock no building, so this property does not apply.
Requirement: the prerequisite research. A research becomes available only once its prerequisite has been completed.
Unlock: what completion grants. Tiers 1 to 7 unlock a specific building; tier 8 researches grant repeatable global bonuses instead.
The Science cost of a research is not fixed. It is computed dynamically from the research's tier, the player's level, and the server's elapsed time, so the cost a player sees in-game will differ from server to server and over the lifetime of a single server.
Research tree
Research dependency tree. Purple nodes have downstream dependencies; teal nodes are terminal (unlock a building but nothing else requires them); amber nodes are tier 8 global bonuses.
The tree branches from two tier-1 entry points, Town Defenses (the military / defensive line) and Apprenticeship (the economic / labour line), and fans out from there.
Tiers 1 through 7 each unlock buildings that cannot be constructed by any other means. Tier 8 does not unlock buildings; it contains repeatable global projects intended for the late game.
Tier
Building village tier
Theme
1
Village
Starter buildings (defence, crafting)
2
Village
Cavalry and organised labour
3
Town
Military, religious and administrative institutions
Tier 8 researches do not unlock buildings. They grant global, repeatable bonuses, and each one can be completed multiple times, with the cost scaling on subsequent completions.