Great Dragon is Gaia Dragoon's Attack Ring (the S-F series one), which has the big wing sub-ring used by Gabriel's base and Guardian Driger. In terms of pictures, uhh, http://homepage3.nifty.com/hind/photo/at...dragon.jpg
(from http://homepage3.nifty.com/hind/sub10-1.htm )
In terms of use, it can be used with Zeus's giant sub-ring for smash attack by fixing it in place, and it's a very good setup, though generally you have to use it in left spin otherwise there are breakage issues (and I'm not comfortable using it even then, because Great Dragon looks really flimsy). Hasbro's Twin Horn apparently works best for keeping Zeus' Sub-Ring in place in right spin without breakage, but there are better uses for that AR and it's not an easy part to replace if it does break.
(from http://homepage3.nifty.com/hind/sub10-1.htm )
In terms of use, it can be used with Zeus's giant sub-ring for smash attack by fixing it in place, and it's a very good setup, though generally you have to use it in left spin otherwise there are breakage issues (and I'm not comfortable using it even then, because Great Dragon looks really flimsy). Hasbro's Twin Horn apparently works best for keeping Zeus' Sub-Ring in place in right spin without breakage, but there are better uses for that AR and it's not an easy part to replace if it does break.