Skyrim modder yourenotsupposedtobeinhere has created a DLC-sized mod that sees you, the now Arch-Mage of Winterhold College, summoned to the Summerset Isles to unravel a mystery, "learning what went wrong, and those whose lives you have touched or tainted along the way."
According to the mod page, there are over 200 hours of new gameplay, 176 quests, 800 plus fully voiced NPCs, a fully-voiced follower, six hours of custom music, seven more player homes, 20 new weapons, 28 additional ingredients, 30 new creatures, a unique travel system, 200 discoverable locations, 137 caves and dungeons, two bosses, 37 new spells, and more.
To start the quest and venture to the Summerset Isles, you must become the Arch-Mage and then travel to the Frozen Hearth where you'll find a courier to speak to. There are a slew of teasers and proof of progress videos on yourenotsupposedtobeinhere's YouTube channel if you want a sneak peek before making the dive. You can see the Azura Quest, for example, below.
It takes notes from Oblivion and Morrowind, but also the base Skyrim, evident above in the dialogue with Azura that replicates Oblivion's echoed voice effect. Besides that, there are "a lot of references" even to titles as far back as Daggerfall, so long-time fans should find plenty to keep them interested. But if you're just after more Skyrim, Summerset Isles will scratch that itch, too.
However, it's important to keep in mind that its approach extends to game design, which draws heavily from Morrowind. So if you're more familiar with Skyrim, it'll be a big shake-up.
"Not all markers will lead to quest destinations, you may have to use your map", the page reads. "You may have to listen to dialogue or read the journal for clues. Some quest progression info is written in books and journals, if you don't read the books, journals or notes, the quests will not seem cohesive. Not all quests are linear, based on how you interact in the quest can determine whether the quest fails, completes or the direction the quest goes."
All you need is 2GB of free space and at least 2GB of VRAM. With that, you should be good to go.