Namesake: Gate of Steiner by Takeshi Abo

「GATE OF STEINER」is an artificial non-humanoid range irrelevant stand. It takes the form of a red smartphone and can be seen by anyone.

Abilities:

First and foremost,「GATE OF STEINER」can function as an actual smartphone, but on top of that, it has three main abilities:

「READING STEINER」

This ability allows the user to observe all changes to the worldline (timeline). For example, if someone were to go back in time and kill someone you know before they met, most people would just have no knowledge of that person. However, with「GATE OF STEINER」you would know that your friend is missing. Another way of putting it, there's a worldline where a can is on a table, if something happens to shift the worldline to one where the can was never on the table, you'd know that the can used to be there.

「D-MAIL」

This ability allows the user to send text messages to the past. While at first this may seem like a pretty boring ability, you must remember that any change made to the past, even something small (like a text message), will change the present ever so slightly.

「TIME LEAP」

The user can send their current conscience back in time and overwrite their past body's mind with it, essentially achieving time travel. This can be used to make slightly more controlled changes to the worldline.

Weaknesses:

All of「GATE OF STEINER's」abilities have a weakness.「READING STEINER」can only see changes that the user already had knowledge of before the worldline shift. You wouldn't know that, say someone dropped a coffee mug halfway across the world in the old worldline, but didn't in the new worldline.「D-MAIL」can only send messages if the target had a cellphone/pager at the time they want to sent the message to, even then the user would need the number of said phone/pager.「TIME LEAP」can only go as far back as when the user first gained「GATE OF STEINER」so you can't go too far back. Another weakness of「GATE OF STEINER」is that some events are fixed in time, and cannot be changed without changing the attractor field (groups of worldlines with similar outcomes), and that can only be done by setting up/undoing a very specific set of circumstances within the previously mentioned limits of「GATE OF STEINER」that's not even mentioning the fact that you still need to find those specific circumstances to set up/undo.

Stats:

Power: N/A

Speed: N/A

Range: S

Stamina: N/A

Precision: N/A

Potential: S