At the core of Assassin's Creed Valhalla, there is an opportunity no other game in the franchise has. Altair was confined to the Holy Land, Connor was confined to North America, and, despite being more world-traveled, Ezio was too confined by his setting. Eivor obviously is too, but thanks to how the Vikings traveled, settled, and raided, her geographical scope is bigger than that of even Ezio.
In Assassin's Creed Valhalla, Eivor travels from Norway to England. She also ventures out to Vinland at one point prior to her death there, where the game seizes the opportunity to really make AC Valhalla a prequel to AC3. This is important not just because she gives the Crystal Ball to Connor's eventual tribe, but how her travels can be used to reference other games. For example, the Wrath of the Druids DLC also sends her to Ireland. There, even, Eivor plays a role in the Viking trade city of Dublin, referencing AC Origins, Revelations, and more in the process.
Despite a record of using Viking travels to establish further connections across the franchise, the aforementioned Wrath of the Druids DLC fails its most obvious connection, Shay Patrick Cormac and AC Rogue. The Easter egg for it there is admittedly a stretch, but hopefully, AC Valhalla has the perfect opportunity to course correct with AC Unity.
Assassin's Creed Rogue: Shay's Easter Egg in Wrath of the Druids
First, it's worth mentioning that an Easter egg to AC Rogue in Wrath of the Druids felt like a given, for a variety of reasons. There's nearly 700 years between the two games, but Shay's parents were Irish immigrants to America. In other words, Shay has connections to the land Eivor steps foot in, but none to Eivor (despite this being similar to the set-up for the AC3 connection). Something as simple as a character whose surname was Cormac would have sufficed to make Eivor and Cormac have some connection, however subtle. It didn't have to set up a new narrative layer as Eivor's travel to Vinland did, but a subtle Easter egg would have been good.
As it stands, although there is really no precedent to go on, it doesn't seem likely that the Assassin's Creed franchise is returning to Ireland, especially anytime soon. The time-traveling and world-hopping nature of the story means there's a lot of other places to be explored, and as the new Assassin's Creed game may no release until 2023, it's unlikely to tread similar water to a DLC. The opportunity to give Shay his nod and wave, as many other games and protagonists did before him, feels like it was passed up.
Notably, there is one small Easter egg AC Rogue fans could point to...if they squint the right way. Scattered throughout the Wrath of the Druids are the Trials of the Morrigan, which shares the same name as Shay's ship in Assassin's Creed Rogue. For fans of the franchise, it may be easy to draw connections based on name alone here, but truly, it doesn't establish much for Shay—it's more of a cultural reference than a direction remark regarding his inspirations. Morrigan, an in-universe Isu, is mentioned in the base game in connection to Stonehenge, but nothing comes of it. Then, in the DLC, her name is brought up with these trials as a potential nod to Shay, but a weak nod if that.
Assassin's Creed Unity: Arno Dorian and Eivor Varinsdottir
The upcoming Siege of Paris DLC will repeat this narrative refrain: Eivor will step foot in a land related to another Assassin's Creed protagonist. As Vinland was to Connor and Ireland was to Shay, Paris and France are to Arno Dorian. Obviously, Eivor will be in France long before Arno is even a thought, just as she was with Connor and Shay. However, because of how important time period and setting are in Assassin's Creed, it too sets up the perfect opportunity for a strong Easter egg.
Where The Morrigan Easter egg falters is that it's just as much as an Irish thing as it is a Shay Patrick Cormac thing; as it stands, AC Rogue could not exist and the Easter egg would make as much sense. In turn, it makes the Trials of the Morrigan a questionable, weak Easter egg at best. This should be avoided in the Siege of Paris, with players being able to connect to or find a strong Easter egg for Arno. Once again, something to do with the Dorian surname could go a long way as a simple Easter egg that is undeniably related to the Assassin's Creed Unity protagonist. However, there is an upcoming opportunity with The Siege of Paris DLC that makes it even harder to pass up on: the addition of one handed swords.
AC Valhalla and The Sword of Eden
If this Easter egg will be similar to AC Valhalla's AC3 connection, then it can be boiled down to a Piece of Eden too. The Crystal Ball is an important Piece of Eden in Assassin's Creed 3, just as The Sword of Eden is in Assassin's Creed Unity. There's two parts of it: The Sword itself and the Heart. If Eivor interacted with either of them, then that establishes a firm connection and Easter egg.
Prior to the French Revolution, the earliest known possession of The Sword of Eden (and forms) were Jacques de Molay, who hid it from the Assassins when he was captured in 1307. And prior to that, though, this particular Sword of Eden has no traceable history in the franchise. It's the perfect crux to bring all of this together: AC Valhalla is going to France and adding one-handed weapons, and the Sword of Eden is a one-handed weapon with connections to France and Arno Dorian. Perhaps Eivor's story reveals how it was discovered (not to mention, she has already been exposed to Excalibur too) or at least ended up in possession of the Templars. After all, its first major appearance was in Templar hands, and the reliable AC Valhalla DLC achievements leak mentions the return of the Order of the Ancients.
All the stars have aligned for Arno Dorian to have a good, strong Easter egg in The Siege of Paris DLC. Perhaps it wasn't in the cards for Shay and that is what it is now, but if Shay was a missed opportunity, not referencing Arno Dorian or the Sword of Eden he once wielded would be a bigger one.
Assassin's Creed Valhalla is available now for PC, PS4, PS5, Stadia, Xbox One, and Xbox Series X.