How do builders work in Dragonfire?

Builders are your construction queues: 1 builder = 1 upgrade at a time. By default you have 2 (2 sites in parallel).

The more builders you have, the more you advance in parallel — buildings plus tier climb — so the earlier you reach Tier 10 in the Reign.

With 2 builders, the trick is to always keep both queues busy: never leave a builder idle. Start the longest job while you sleep, and the short ones during the day.

The third builder (a paid offer, around €9.99) is permanent (it doesn't reset between Reigns) — the only durable lever on the Stronghold side. See the dedicated article.