The character you choose to play as will affect the powers and abilities that you can use to tackle each assassination. Though we didn't see any of Corvo in Dishonored 2's announcement trailer, it's safe to assume he'll return with his signature Blink power, which allowed him to teleport short distances.
Instead, we got a look at the powers Emily Kaldwin will bring to missions. Instead of Blink, Emily can use a kind of magical grappling hook whereby her arm extends forward and pulls her to her destination. She also possesses what looks like the ability to turn into a shadow and move along walls, a power called "Shadow Walking" that was cut from the original Dishonored. Of her weapons, we only saw a glimpse of a crossbow, as well as an Arc Mine, a weapon that was added in Dishonored's DLC, The Knife of Dunwall. Emily also picks up what looks like Corvo's signature retractable sword.
Dishonored 2 takes place in Karnaca, a city located on the continent of Serkonos to the south of the original game's setting of Dunwall. Karnaca is notable for being the birthplace of Corvo, as well as the source of "corrupted" Bone Charms, passive upgrade items with both positive and negative effects also introduced in The Knife of Dunwall DLC pack. In a change from the city of Dunwall, Karnaca features what appears to be a greater blend of both urban and natural environments, including brighter, warmer locales. Technology seems to have advanced, too, with Emily seen fighting robotic enemies.
The trailer featured the voice of The Outsider, the supernatural entity who originally gifted Corvo his powers. His ambiguous commentary and playful neutrality appear to permeate the tone of the story, which sees the Empire of the Isles under siege from a new political threat.