Saucer Organism No. 1, Silverbloome came from Black Star, which lies ten million kilometers from Earth. It was summoned by the Black Directive, who plotted to erase Ultraman Leo along with all of humanity. Silverbloome mainly attacks using a corrosive liquid and its countless long tentacles.

Silverbloome began its attack with an assault on the MAC base in Earth’s orbit. It swallowed the base whole, wiping out MAC out. Only Gen Otori escaped and was able to transform into Ultraman Leo, but Silverbloome shook off its pursuit and flew to Earth. Silverbloome engulfed central Tokyo, killing many including Momoko Yamada, Toru Umeda, and Jonan Sports Center’s Takeshi Nomura.

Silverbloome then shrunk down into the form of a small saucer and hid in the city. It was found by one of Toru’s classmates. Their school teacher tried to experiment on it, so Silverbloome consumed him with its corrosive liquid. After that, the Black Directive caused a storm to appear and Silvebloome returned to giant form to attack the school.

Ultraman Leo arrived and Silverbloome attacked him with its tentacles and acid attacks, but was blown to pieces by Leo’s Spark Beam.