i just finished teh rotting dino guya nd got the powerful beam and now i dont know where to go

If you just finished of Gergoth, next you nedd to go fight Zephyr. get back to the top of the tower (with the help of the flying armor soul) and go to the tall room beneath the warp room.(warp room located next to the place you began the fight with gergoth)in the middle of the room on the left side theres a path. Go that way.

P.S.- there is a girl from earlier in the game on your way there but, don't near her. It's a fake. slash the crap out of the mimic.

ok i went there but cant get thrugh becasue there is a blue gate or door thing in the way and i cant get through and i already tried teh beam how do i get through it?

Go to the very top left room, there will be a key there to open the blue door.