The Big Mother is a large Dark Gaia Minion that appears as a sub-boss in several nighttime stages of Sonic Unleashed. These creatures are so named due to their ability to spawn smaller Dark Gaia monsters.
The Big Mother stands about four meters tall, with oxford blue and cyan skin with magenta glowing markings. They have a dopey look to them and have a large belly with a large mouth stretching across it. They have rather large feet, with the upper parts of their legs covered by their stomachs, and long sleek arms. They have no visible neck and they have curved spike-shaped appendages on their shoulders and upper backs, and horns on their foreheads.
In battle, Big Mothers tend to hang back and continuously birth Little Rexes to do the dirty work. They will normally spawn between 6 and 8 at a time, only birthing others when Sonic has destroyed any that are already on the battlefield. If Sonic gets close enough, the Big Mothers will attack directly, using their arms like clubs and smashing them into the ground. They can also create shockwaves by doing this. As well as possessing great physical strength, Big Mothers are highly durable and cannot be easily stunned. Only the Werehog's most powerful attacks are capable of stunning these beasts.