Once you turn lvl 99, I forget what town you go to but you go talk to this old guy and he gives you the Juggernaught seru :) I remember using gameshark to reach lvl 99 just to see how badass this seru is..and yes, he is quite badass.
they say stone cold killas have the prettiest eyes im goin 5150 inside they say stone cold killas give a **** if u die if lifes a (b) ima kiss her goodbye MUAH
Yes. After you go to level 99 just go back to Ratayu and talk to Bon Saryu, he will say something along the lines of "wow, you look much stronger than before, I believe I can trust you with this." then he gives you the key to the underground basement where the seru brides were being held. At the end of the long path there will be a talisman that you can give to Zalan and he will enable you ot do the Juggernaut summon, which is called "Dark Eclipse."
I do not see why man cannot be just as cruel as nature. (^_^)