Oh, shut up and help me remodel the Ultimate (Final Fantasy XIV) page!
Ultimate duties are a type of duty found in Final Fantasy XIV. The Ultimate-level duties are high-end raid duties that host a gauntlet of bosses from previous raids or trials, and are intended to be of even higher difficulty levels then the Extreme or Savage levels that previously represented the game's hardest content. These fights require players to have completed the Savage difficulty-level of the previous raid section to even unlock. Due to its high difficulty, Ultimate content is not intended to be "progression" content for the majority of the player base, and is designed solely for those seeking a challenge.
Ultimate content has thus far been strictly recreations of older content, with the Unending Coil of Bahamut being based on the Binding Coil of Bahamut raid series, The Weapon's Refrain being based on the climactic battles of the A Realm Reborn main storyline, and The Epic of Alexander being based on the Alexander raid series.
Unlike other content, the development team currently has no plans to increase the Level or Item Level syncs on Ultimate content, or allow the older duties to be run unsynced. This is in order to preserve the difficulty level as it was when initially released, even as players become more powerful as the game progresses, and ensures that all Ultimate content, both existing and forthcoming, will remain the hardest content for the remainder of the game's lifespan.