Steel

Steel (スティール) is a Quirk used by Tetsutetsu Tetsutetsu.

Description
This Quirk allows Tetsutetsu to turn his body into steel.

Steel is tough enough to protect Tetsutetsu from bullets and tons of falling metal, as well as other lethal hazards. Tetsutetsu has said that he will gain longer and stronger use of his Quirk depending on the level of iron in his diet. It is unknown if this refers to foods that have iron in them or if he has to eat the actual metal.

Steel makes the user completely immune to extreme temperatures. Tetsutetsu can break out of Shouto's ice after being frozen without having to worry about his skin tearing off, since it's steel. He is also immune to very high temperatures, in fact it makes him stronger since the steel itself will get very hot and makes his attacks stronger.

Using his Quirk for too long will cause Tetsutetsu to suffer from iron fatigue, gradually weakening Steel's hardness. Steel also doesn't protect Tetsutetsu from all forms of damage, as poisonous gas can still be effective.

Usage
Very much like Eijiro Kirishima, Tetsutetsu is extremely straightforward and reckless, taking fights up close and letting his Quirk protect his body from harm as he dishes out counterattacks. Also, similar to Eijiro, Tetsutetsu is able to turn himself into a human shield, blocking attacks meant for his allies.

Trivia

 * This Quirk is very similar to Hardening, but turns the user's body into steel instead of just hardening the skin. The two also appear to be roughly equal in terms of power and effectiveness.