The Sonic Twitter posted this a few days back.
Cipher says:
Hugo is the real name of French artist Madeon. The image itself is a parody of the cover for Madeon’s “Adventure” album. The obvious idea here is Sonic Adventure 3 (!!!) but there’s more clues in the image, possibly to the game’s plot.“Hello Hugo
The secret is inside the empire.
We can get it back.
The fated son of Daedalus.
Add the numbers.”
“The secret is inside the empire” could potentially be referring to the Eggman Empire? Not sure. Same with the next line.
“The fated son of Daedalus” is most definitely a reference to Shadow. In Greek mythology, Icarus is the son of Daedalus, who built his wings in a tower. He flew too close to the sun and his wings burnt up, causing him to fall. Shadow was created in Space Colony ARK, and after the battle with Finalhazard, he fell to Earth.
The tags on the Tumblr cross-post include - “verse un, line dix et line douze”. Lines 10 and 12 of the Madeon song “Nonsense” are as follows:
The first line works as a general Sonic reference, whereas the second is very obviously a Sonic Adventure 2 reference - Eggman fired a warning shot at the moon with the Eclipse Cannon to strike fear into the nation.“And don’t you think that I’m a runner”
“Shooting at the moon to bring the sun up”
Someone on 8chan realized the meaning behind “Add the numbers” - if you add every number mentioned in the Sonic Tumblr’s posts and tags from the initial 25th anniversary post up until the day of the teaser being posted, you get 98 - 1998 is the release year of Sonic Adventure in Japan.
Additionally, 25th anniversary advertisements have been surfacing in various locations with the tagline - “Join the Adventure”;
Discuss.