Blade the Hedgehog is a fan character specifically designed for Super Smash Flash, a game created by McLeodGaming. Additional details on this character have not been implied by his creator.
In recent years, more information was about the character was revealed. He was originally created by a Newgrounds user named Equinox-Twilight, who was inspired by another Sonic OC named Flare the Hedgehog (implied to be Sonic's "brother"), a character that appeared the KA Omake Flash animated series that was also created by the same user. McLeodGaming was gaven permission to use Flare's template sprites and had Topcat13 redesigned the character to be "different" from him and came up with the name Blade, athough it has not confirmed whenever this is true or not. Super Smash Flash was originally a platform action game starring Blade as the protagonist and he was added for testing purposes. Overtime, the design was fully established. He was set to appear in Super Smash Flash 2, but he was officialy cut along with other fan characters.
In The All-New Spursverse, he will be "fleshed out" with a backstory and other factors that are important to the development of a character.