Hundreds of people attended the latest Silicon Colosseum event, an underground robot fight club in San Francisco’s SoMa neighborhood, where mechanical competitors battled inside a caged octagon.

Tickets sold out at $30 each after an online invitation went out to about 2,000 people, drawing a crowd eager to watch robots — and even some staged human “Taser knife fights” — compete.

The star of the night, a humanoid robot named Booster, faced off against larger robots, including a bipedal dog-like machine, thrilling the audience with its ability to right itself after being toppled.

The event was organized by 20-year-old Verda Korzeniewski, a former robotics engineer who left the industry to pursue her vision of a robot fight club, now in its second showcase after debuting in July, Fox 56 News has reported.

Korzeniewski plans to hold another underground robot battle in November, though the location remains secret.