thou art mortals unlike me - Not only is he a GF, he is a God in Norse(?) Mythology.
through twists and turns you shall seek - Referencing the crap you go through with the demons etc to get to him
time against you, the eyes you sought - Once again, the demons' eyes and the countdown
the beast stands proud.. tall
on more legs then four - Referencing Sleipner or whatever Odin's mount is called which has six legs.

make haste for i will not show mercy - Just be quick? I don't know if he tries to use Zantetsuken or not
for when i visit be sure too know - Dunno again
the end is nigh, 3 moves and off i go! - If the battle with him ends after three rounds, then that. But if it references the 3 characters that make up Zantetsuken, then that

who am i? - ODIN