Cantha will feature a lot of nostalgia not only for Guild Wars players but the veterans of Guild Wars 2 as well. Aetherblade Hideout is one such example.
Guild Wars 2 players haven't faced the steampunk-ish band of rogues going by Aetherblades in a long while, despite their prominent role in Scarlet's campaign that resulted in the destruction of Lion's Arch. Those who remember those days of the Living World will know that Aetherblades, and most importantly - Mai Trin, were messing around in the Mists at the time we took the annoying Sylvari down.
Just like the name suggests, Aetherblade Hideout will have us wiping floor with their asses once again, in the form of the new Strike mission. Speaking of which, the Strikes have a somewhat different format this time around. In End of Dragons, they will basically be just boss encounters from the main story but they will be beefed up for 10-player challenge and serve as an introduction to the mechanics of the complex bosses encountered in raids.
Ramping up the difficulty will not be for nothing. Strikes will have their own rewards, once again offering the players a way to express themselves through the Fashion Wars. Like before, there will be the challenge mode for the most coordinated teams that can take these enemies down for the ultimate bragging rights and possibly cosmetic variations on the aforementioned gains.
While this may sound like a lot of new info and possibly like spoilers, you might want to hang on to your seats until you delve into the hideout yourself - Anet prepared more than a few moments to make you go "Oh wow".