170,000-Year Magicicada Nymph is a large Mysterious Being that attacked Z-City at some point during Saitama's training years.
Appearance
The Magicicada Nymph is a massive cicada, that has the face of a child located at the center of its head, between its eyes.
Plot
During Saitama's training years, Nymph attacked Z-City and defeated two C-Class heroes, Grad School Graduate and Red Muffler, and a B-Class hero, Darkness Blade, with ease. Sometime later two unnamed A-Class heroes try to fight it but are also defeated. This causes the Heroes Association to declare it a Demon level threat and they are sending some newly built subjugation squads to kill it but while Saitama was running towards a bathroom, he saw the beast and killed it with one punch.
Abilities
Nymph strong is Demon class in the Heroes Association and show to take out C-A Class with ease.
References