I was on and saw that there is a mythic difficulty. In order to unlock it you have to beat the game on SLASO(solo legendary all skulls on). I think it would be impossible because you cannot die even once with iron (skull) turned on. Also another skull makes it so the only way u can heal is to beat someone to death. another skull that would make it really hard is famine i think...it makes them has twice the health(if u ask me its like 10 times the health because on legendary with this it takes 5 headshots to kill the weakest type of brute wit sniper rifle. Last but not least...blind...the skull i hate the most. It does exactly what it sounds like. You can see the screen and everything but you cannot see your aiming device, radar, ammo, health and all that stuff...its just complete blank besides the accual map and everything.
So all u Halo 3 players good luck at that(i dont think it will ever happen...anyway it could be a myth)
well it is "mythic" difficulty, so it could be a myth. however, turning on all of the skulls and playing the game on legendary seems much harder than just regular legendary mode. maybe by beating the game with all the skulls on on legendary would be considered beating it on "mythic" difficulty. if not, then it is probably a really hard difficulty level that is almost impossible to achieve.