Grant X is the version of Grant you fight on Solitude to seal the gateway to stop the dark knights from entering the world. You can fight him again in the dicktionary by renting a room with him. His weaknesses don't save though, since he has multiple positions per wave, so you'll need the guide for them to play perfectly. It's on another one of my posts here on the community page.
Viewing post in Secret Quest Guide [version 9.X]
try to use some kinds of dishes like strange fish curry & orc's favorite dish (can be purchased at valdo's home). i used fish curry in beginning of fight then the orc's fav one in late fight (when my hp almost reached 100%). It worked for me, of course along with those equipment, scrolls, & super effective moves you mentioned. have fun.