From the announcement:
Generals rejoice! The STRONGHOLD expansion is now available for download on Wargame Vault.
The new material has been combined with the core rules to create the Battle Chest edition. What does this mean? It means that all of your content is available in a single convenient location. Not only that, but for players that have already purchased MAYHEM, all you need to do is return to Wargame Vault and download the updated version of the rules completely free of charge! So, what's in the expansion?
The STRONGHOLD expansion includes rules for:
advanced terrain options including the garrisoning, attacking, and burning of structures
new designations like scout, skirmisher, and heroic skirmisher
heroes to engage one another in epic challenges
battle sorcerers that can focus their magical powers to control hulking mechanical constructs or harness the fury of bound behemoths
new spells, traits, abilities, and gear
building your own strongholds and keeps including over 15 upgrades to create the ultimate fortress
siege engines and laying siege to enemy strongholds and keeps
new scenarios including border keeps and a unique mass battle multiplayer mode
campaigns and linked games with unit progression, multiple paths to victory, and seasonal weather effects
The expansion has been set-up as a toolbox that will allow you to pick and choose the rules that best fit your group and the gaming experience you're looking for. It also means that the core rules will grow and evolve along with your tactical and strategic abilities.
Have fun storming the castle!