Paradox Interactive now offers Mare Nostrum, the new expansion for Europa Universalis IV, their grand strategy sequel. They say this adds a bunch of improvements and updates to the game, with a particular emphasis on naval operations. This previously released trailer offers a look at the add-on and offers thoughts on it from designer Johan Andersson, and you can find more details on the game's product. section. Here's word on the expansion and an accompanying patch for the base game:

Mare Nostrum is the newest expansion DLC for Europa Universalis IV, Paradox Development Studio’s best-selling grand strategy game set in the adventurous days of the Age of Exploration, the Renaissance and the wars of Reformation and Revolution. Mare Nostrum adds a number of improvements and updates to the game, bringing more control and detail to the naval game.

Features include:

• Naval Missions: Naval interface improved to make control of your fleets less hands-on and more mission oriented
• Barbary Raids: The Berber nations of North Africa can raid their neighbors for money and extra sailors
• New Espionage System: Build a spy network and call on it to undertake actions in enemy lands
• Trade Leagues: Merchant republics can recruit minor nations into their Trade League for common defence and, more importantly, common riches
• Condottieri: Rent out your army so it can fight someone else’s wars while you earn gold

And, as always, the expansion DLC is accompanied by a massive update that is free to every Europa Universalis IV player – even if they never buy Mare Nostrum. This update will include an updated map, a new state system to organize your nation, tweaks to naval combat and the introduction of sailors to man your ships.