Black Ooze (ブラックウーズ?) is a recurring demon in the series.
In the Dungeons & Dragons fantasy role-playing game, an ooze is a type of creature. This category includes such monsters as slimes, jellies, deadly puddings, and similar mindless, amorphous blobs. They can be used by Dungeon Masters as enemies or allies of the player characters.
Many oozes dwell underground, and most secrete an acid from their skin that dissolves flesh and other materials rapidly.
Oozes are essentially blind, but more than make up for that with an ability called "blindsight", which allows them to discern nearby objects and creatures without needing to see them visually.
"Origin: Unknown. A body of black muciferous gel. This demon failed to materialize and lost control of itself, thirsting for blood."
—Shin Megami Tensei A-Mode DDS Dictionary
Shin Megami Tensei III: Nocturne
"A mass of malevolent intent and emotion that failed to become a true demon. All it does is eat prey and grow."
—Shin Megami Tensei III: Nocturne Compendium
Black Ooze can be found in the Asakusa Tunnel. It will sometimes drop Medicine after a battle.
Shin Megami Tensei IMAGINE
"A mysterious being of unknown origin. Its body is a mass of pitch-black, viscous liquid. It swallows all creatures that draw near, growing ever bigger as it does. The Black Ooze is said to be the form of a demon who failed to achieve its true form and can no longer retain its shape."
—Shin Megami Tensei IMAGINE Compendium
Black Ooze can be contracted during the day in Ueno and within Suginami Tunnels' silver-level instance. It acts as one of the three bosses in DB Watanabe and DB Saitou's hacked chip instances. A large nightmare variant can be encountered in the basement levels of Old Ichigaya Camp.