The Nord is shown at the start of the trailer fighting a zombie werewolf. At the end of the trailer, we see one of the werewolves burst out of the ground in an attempt to flee, only to be dragged back under by the Nord, who climbs out a second later.
Fridge Brilliance: It also shown how good the Ebonheart's (specifically Dunmer's) intelligence service is as they successfully track and locate the hidden tunnel under the fort while two other forces have to climb the cliffside, not knowing the tunnel's existance.
Though we finally understands why the tunnel is abandoned (and the information about it is not closely guarded) in the first place, as it's swarmed with undead werewolf. Attacking from there may shock the defenders but it's not justifying the trouble.
The Breton commander who pulls off acrobatic feats and kills a squad of solders in a manner that would make Altair gush.
The Altmer commando treating the gigantic melee and siege she's navigating through with appropriate Altmer disdain. She'll need more than a nigh-unkillable Nord badass and a spinning top of death-dealing Breton in her way to properly inconvenience her...
The Arrival Trailer. showing the three leaders from the Alliance trailer having to fight a platoon of dremora. It shows how much of a threat that they'll be, because the Breton ends up possessed and attacking the Imperial City with a army of undead while the Nord and Altmer barely escape with their lives.
This trailer really belongs to the Altmer Mage who holds her own against well over a dozen Dremora using her sword and truly impressive magical skills and she's the one who destroys the Dremora portal single handed. The Nord also puts in an impressive showing by looking at the biggest enemy in the room (a 20 foot tall flesh monster), then charging right at him and actually managing to hold the advantage for the first half of the fight until the addition of a few tiny Scamps turns it less in his favor. The Breton sadly gets beaten by a Dremora wizard before getting turned into a zombie. The video ends with the Nord digging up the unconscious Altmer from the rubble and carrying her as POW.
The Siege Trailer, Ebonheart Pact lay siege to Imperial City. They channeled captured Altmer Mage' magicka to split wall of city using magic, their forces then charging straight to hordes of Imperial City's undead. After opening the wall, Altmer Mage then broke her own chain and fight her captors in terrible conditions. Meanwhile, The Nord determinantly goes Straight for the Commander as The Zombie!Breton's arrows take down his Argoinan companions. Showing they are just Red Shirt-s tailing the Nord. The trailer ends with The Nord facing The Breton to settle it once and for all.
Fourth Trailer, Nord facing Breton on one-on-one duel. Breton scoring few hits on Nord but kept brushing those. In summary, Mighty Glacier beats a Lightning Bruiser.
The entire Morrowind Announcement Trailer. However the most spectacular moment goes to the final shot of Vivec with Baar Dau stopped above it. Followed by a new version of the beloved Nerevar Rising version of the Elder Scrolls Theme and the titles.
The Summerset Trailer. We finally get to see Alinor, and it's beautiful. There are also several shots of mysterious shadow-figures in the background, which closer inspection reveals to be the Daedric Princes Mephala and Clavicus Vile, along with one shot of Nocturnal atop Crystal-like-Law.
Defeating Molag Bal himself in a one-on-one battle certainly counts as one for the Soulless One.
The good endings to the Harpy sidequest in Glenumbra. Instead of allowing the corrupt lord who hired you and a mercenary company to get away with instigating the harpy attacks for his own profit, you convince the mercenary company to stop the lord, money be damned. In the end, the Orc who travels around with you releases a caged harpy that then proceeds to kill the lord. And you end up getting paid anyway, because they found a cache of gems in the lord's possession.
On a meta level, the justice system that will be coming out allows players to go on murder rampages and rack up bounties.
The main questline for Summerset has numerous moments which count.
Many characters make a return in this expansion, such as Razum-Dar, Rigurt the Brash in a sidequest, Veya Reloth from Morrowind, Andewen in another sidequest, and Darien Gautier, who was presumed to be dead after the events of Coldharbour.
Defeating Nocturnal herself while armed with the Dawnbreaker. Assuming the player defeated Molag Bal already, it means the Vestige has defeated two Daedric Princes in combat now.
If one does the side quests of the expansion before finishing the main quest, it actually ends up paying off. During the Council meeting after Nocturnal's defeat, the Sapiarch there condescendingly asks what have you done for Summerset. Cue several characters you've assisted while journeying throughout Summerset coming in to vouch for the good deeds you've done and forcing the Sapiarch to acquiesce to what they say. Even more are waiting outside in the main hall for you. Doubles as a Heartwarming moment.
In Murkmire, you can find dossiers for some of the main characters, with information about them and how best to kidnap them. There is one for you, the player, as well, titled "the Newcomer". The recommended approach? No less than twenty men, attacking in force. Even then, the dossier says the player might be too strong, and that anyone who wants to try taking on the player, does it at their own risk. The player is certainly building up a reputation.