Egg Hammer Fortress has an appearance is similar to Egg Hammer Mega, which body appearance is a snake or anaconda. The white on top of its head is where an Egg Mobile is located. Depending on the character you chose from depends on the color scheme it has.
Sonic: It has an green head, white and orange striped body, orange like-fangs, and gray spikes on the neck.
Blaze: It has a yellow head, green and cyan striped body, green like-fangs, and gray spikes on the neck.
Like Egg Hammer Mega, it throws its head down on the ground aiming at Sonic/Blaze's position as its main attack. However, this boss adds a twist; the Egg Hammer Fortress may slam its head three times in a row on the ground before stopping for Sonic/Blaze to attack its head. Its 'killer head slam' (when Eggman/Nega says 'Get ready to be schooled') will actually aim for Sonic/Blaze as opposed to remaining still in Egg Hammer Mega's battle, meaning this attack is by far harder to avoid and in many cases, the player will not be able to strike back the Egg Hammer Mega after this deadly attack although it is possible. As the battle progresses, it will travel to the rear section of the ship's background and drops its head to activate the ship's gun cannons to fire at Sonic/Blaze. Once hit six/eight times, the Egg Hammer Fortress is defeated.
In normal difficulty, aside from requiring eight hits, its "triple head slam" attack will move towards Sonic/Blaze when it has taken enough hits, which can be fairly troublesome if Sonic/Blaze is cornered against the edge of the platform.
It is the only boss that uses the same attack and model design as Egg Hammer Mega, a boss from Sonic Rush, as well.
A very early in-production picturing showing Sonic fighting the Egg Hammer Mega used the background that this boss uses.