Here is an overview of the expansion, via its Steam page:

Begin a unique adventure filled with the unparalleled storytelling and deep lore of The Elder Scrolls. Journey to Tamriel—a living, breathing, fantasy universe of magnitude, where your choices shape your experience. Battle, loot, craft, steal or role-play as an archer, mage, merchant, scholar, or warrior. Play solo or with friends and combine equipment and abilities to suit your own play style. No game subscription required—buy once, play anytime.

Key Features

• Unlock the New Class – Become empowered by the secrets of Apocrypha and the forbidden knowledge of Hermaeus Mora. The Arcanist is a powerful new Class capable of destructive, restorative, or defensive magic by channelling the arcane, ancient runes, and lost tomes of power.
• All-New Zones – Explore the Telvanni Peninsula, home of colossal mushrooms, arcane magic, rocky spires and the capital city of Necrom, additionally, behold the forbidden books of the endless library of Apocrypha.
• A Cosmic Story – The Prince of Fate holds secrets too dangerous for mortals or Daedra to comprehend. Now hidden yet turbulent powers threaten Hermaeus Mora’s realm of Apocrypha and if the Daedric Prince’s secret is uncovered, it could unravel all of reality.
• New Warden and Arcanist Class Companions – Two new allies seek grand quests and glory! Unlock the Arcanist-power-wielding Redguard and Argonian Warden Companions to battle by your side and keep you company on your journey across Tamriel.

Collection

Pre-purchase The Elder Scrolls Online Collection: Necrom or The Elder Scrolls Online Deluxe Collection: Necrom to get instant access to all major Chapter zones, biomes and quest arcs from across Tamriel. The Elder Scrolls Online Collection: Necrom and The Elder Scrolls Online Deluxe Collection: Necrom includes the base game, “Necrom” and all previous Chapters, as below (plus Deluxe items for those who get the The Elder Scrolls Online Deluxe Collection: Necrom).

• “Necrom” (NEW for 2023, unlocks in June)
• Unlocks instantly:
  • High Isle
  • Blackwood
  • Greymoor
  • Elsweyr
  • Summerset
  • Morrowind
  • Base game

Those who pre-purchase The Elder Scrolls Online Upgrade: Necrom or The Elder Scrolls Online Deluxe Upgrade: Necrom will receive the “Necrom” chapter—or “Necrom” chapter and Deluxe items, respectively—these versions do not include the previous Chapters or the base game.

Read more about the expansion through the following links:

Watch a new set of trailers below.

Cinematic Trailer