Pictured: Knuckles commencing his new Neutral Special by digging a hole in the ground.
Knuckles the Echidna is a member of the Sonic cast that debuted in Sonic the Hedgehog 3 in 1994. Besides being very fast (like most Sonic characters) he has a variety of additional abilities such as super strength, enhanced durability, the ability to wall-climb, glide, burrow and manipulate the earth.
While most of those abilities were represented adequately in Crusade we felt that there were ways we could expand on that representation by adding abilities that have appeared in canon material. One of these abilities is digging which now is his neutral special, allowing him to burrow within the ground and emerge for a powerful uppercut!
His boulder throwing attack has also been upgraded! Being his side special the boulder can be thrown in any direction with greater ease, including while Knuckles is airborne!
As a result, Knuckles now uses the same button input as all other Sonic characters in Crusade to spin dash (Down Special).