Mysterious Cubes

These are a series of cubic objects that are used to communicate with "God".

Overview
According to Blast, the cubes act as a transmitter that distort space and allow for communication with "God". Anyone who comes in contact with a cube is able to hear the voice of "God" in their head.

One of the cubes was first seen 18 years ago during a flashback of Tatsumaki when she was saved by Blast from a hybrid monster. Another cube was also found by Saitama, Manako, and Flashy Flash in the rubble of the Monster Association Headquarters. Blast stated that there are multiple cubes scattered around the world, and that he has been collecting them as a hobby.

Abilities
The cubes appear to be extremely heavy, as one was able to get Flashy Flash's arm stuck, and sunk into solid rock after being dropped by Saitama. Additionally, Manako was unable to lift it back up.

The cubes have the capability to turn humans into Mysterious Beings, as in "God" can grant powers to those who place their hands on one of the cubes whilst stating their wishes. However, if said individuals are not worthy to be bestowed upon, they will face "forfeiture", with the mysterious entity presumably killing them. It is unclear how "God" deems someone worthy of receiving its powers.

Monster Association Arc
One of the cubes appears for the first time during Tatsumaki's flashback as she recalls the events of 18 years ago when she was saved by Blast from a monster. It is revealed that Blast was holding a black cube when having a conversation with Tatsumaki at the time.

Later, when Saitama and Manako are helping free Flashy Flash, they come across another cube which had pinned Flashy Flash's arm down. Saitama inspects it before throwing it away without having any idea what it actually is. As Tatsumaki begins to lift the remains of Monster Association Headquarters into the air, Saitama along with Flashy Flash and Manako peer out into the hole expecting to see the underground, only to instead be greeted by a black void, with a mysterious figure sitting prone inside, though the three cannot see it.

God's voice begins to speak in their heads, saying that if they touch the cube and make a wish, the being will either grant them power, or they will face "forfeiture." Immediately afterward, Blast appears and is relieved to find that the group did not accept God's words. He takes the cube, transferring it through a portal to an unknown location.

Psychic Sisters Arc
Shortly after the raid on the Monster Association Headquarters, several S-Class heroes who were involved are summoned to an emergency meeting with Sitch and Sekingar to discuss the unexplained phenomena that were witnessed. In the discussion, "God" is brought up and Flashy Flash mentions his encounter with something that could communicate directly into his mind. He mentions Blast in passing and questions Sitch about what he is hiding based on how Blast asked him to send his regards. Sitch comes clean, admitting that Blast had been fighting "God" for 20 years now and along with some collaborators had been searching for these mysterious cubes that could enable communication with "God". During this time, Blast and others had also been collecting and analyzing them. Sitch further states that Blast had a direct encounter with "God" two years ago while battling Elder Centipede and after refusing to accept a transaction of power from "God", the top hero engaged in battle with the mysterious entity and managed to survive.

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