Gigantic (ギガンティック Gigantikku) are one of the four tribes from the Red World.
Z/X Encyclopedia Entry
The name for huge beasts created for the sole purpose of being imaginary enemies to push the Braver to even greater heights. When they detect signs of Braver, they move in to slaughter them, but this is a command implanted as a form of instinct, not something they intend to do.
Because they are lifeforms created from silicon, they are beast-shaped entities with a rock-like or ore-like quality to them. Because a different institute, separate from the one that made the Braver, made these creatures, in recent years, the institute has forgotten their original purpose of doing it in the spirit of rivalry, and now are bent on only creating a stronger Gigantic. As a result of repeatedly evolving and improving, Gigantic have finally begun to appear that transcend even the Braver.