http://www.eyesonff.com/kh/walk18.shtml Scroll down to Coliseum Section

You get the Yellow Trinity after you beat Hercules *Hercules Cup* in the Coliseum Matches and Yes, they do get stronger

Here: http://www.eyesonff.com/kh/walk12.shtml Pegasus Cup help *Scroll Down*

Here: http://www.eyesonff.com/kh/walk18.shtml hints on Olympus Coliseum Bosses after the Pegasus Cup *scroll Down*

the walktrhough is on the front site at this link: http://www.eyesonff.com/kh/index.shtml

And the Key hole at Wonderland? I don't remember there being one. I hope this help :P