For all I know this hard mode could range anywhere between super basic Ganondorf amiibo in TPHD and really changing gameplay SS Hero Mode style. (gonintendo.com)
Check out the reveal trailer for Ganondorf as a playable character in the other video posted above. (heavy.com)
Sometime after the sealing of Ganondorf in the Adult Timeline, he eventually broke of his seal and once again terrorized Hyrule. (zelda.gamepedia.com)