The Elder Scrolls Online made it clear back in December that its next year of DLC and story content would be Oblivion-themed with a not at all subtle teaser trailer for the Gates Of Oblivion storyline. They've gone and revealed more details about the expansion called The Elder Scrolls Online: Blackwood, which will add a new explorable zone by the same name, Oblivion gate world events, and a companion NPC system.
Similar to last year, TESO has given the name Gates Of Oblivion to the overarching story for the year in which you'll "unravel the ambitions and schemes of the Daedric Prince Mehrunes Dagon 800 years before the events of The Elder Scrolls IV: Oblivion." As with 2020's Skyrim storyline, it's broken up into releases throughout 2021. The Flames Of Ambition DLC is scheduled for March, with the Blackwood expansion arriving in June. Two other DLCs—a dungeon pack and a story zone—will arrive later in the year.
The Blackwood expansion in June is the central release, bringing a new explorable zone with its own quests and storylines. Blackwood will include familiar city Leyawiin from Oblivion along with the Niben Forest and Blackwood Bog. It will also add Oblivion gates that pop up around the map as world events for players to tackle together in the open world, and a new 12-player trial.
Most interesting to me, the forever solo player, is the new companion NPC system that Zenimax mention. They say that companions can be recruited to follow and fight along with you and have their own stories as well. "These unique warriors can join you in almost all of your adventures, level up their skills, and use customizable gear and combat abilities and behaviors," they say.
I suspect more combat competent players will have their concerns about companion AI and the ability to customise it exactly to their liking. Admittedly, I'm the type of player who will probably be happy with a meat shield who has a story. Zenimax's description of the system does bring back memories of ye olde original Guild Wars's hero characters, a feature I really miss as a loner MMO player.
You can catch a bit more about Zenimax's plans for the first half of the year in their announcement post about Blackwood. For PC, Mac, and Stadia players, the first DLC of the year will arrive on March 8th and the Blackwood expansion itself will launch on June 1st. For console folks that'll be March 16th and June 8th respectively.