Energiser

Energira (エネルギー, Enerugī) was a monster located in the uninhabited area in Z-City in the audiobook, "Sonic, becoming Saitama".

Personality
Energira is confident in its abilities but is still cautious. He recognizes that there are beings stronger than itself and will go into hiding to avoid attention.

History
Energira is a powerful monster hiding in Z-City’s uninhabited zone. He is discovered by the Hero Association and is targeted for an attack.

Sonic, becoming Saitama
Tornado of Terror and Atomic Samurai are tasked to eliminate Energira, but Speed-o'-Sound Sonic, disguised as Saitama, encounters the monster first. Sonic struggles to fight the monster. Fortunately for Sonic, Saitama arrives and, together, they easily defeats the monster.

Abilities and Powers
Energira fought and would have killed Speed-o'-Sound Sonic had Saitama not intervened.

Physical Abilities
Immense Durability: Energira took on several of Speed-o'-Sound Sonic's shurikens without any damage.

Supernatural Abilities
Energy Projection: Energira has the ability to compress energy and emit them from his hands. The monster has limitless energy stock although it needs time to build energy blasts up.

Trivia

 * Energira is the only monster Saitama and Speed-o'-Sound Sonic teamed up on to beat.