How does the Heirs of the Dragon campaign work?

The "Heirs of the Dragon" campaign is the Reign's major story event: 11 chapters plus an epilogue, over roughly 40 days (the length of a Reign).

Structure:

• Each chapter opens objectives to complete and unlocks rewards.
• You progress by doing normal game actions (conquering castles/capitals, dealing siege damage, and so on).
• Key constraint: you must reach Stronghold Tier 10 before the end of the campaign, or you can't finish it.

It's a big source of rewards (keys, Relics, gold, resources) spread across the whole Reign. The right reflex: follow the campaign continuously rather than doing everything at the end — some chapters take time (Stronghold climb, conquests) and you don't want to be stuck 2 days from the deadline.