I started the 'Garden of Eden' thread, not realizing that this has already been discussed on previous threads. :rolleyes2

Oh well. I think it's an organic version of the SeeD gardens. Like Knights of the Round in FFVII,it is the ultimate summon attack and by far the most over the top in apperance and damage.

Maybe it's some final form or incarnation of a Garden. It's not uncommon to reveal a machine/building is actual a living entity, ie ST:TNG 'Encounter at Farpoint', or one of the Mortar Hedds in 'Five Star stories'.