Frost

Frost belongs to Rei Todoroki, and through her to the second and third of her four children. The power itself is modest in scale next to the fire it was bred against, but its presence in Rei's genes is the reason the Todoroki household exists at all, and its ice ultimately proves decisive in the family's final crisis.

The ability was never given a name across its manga appearances. Only the anime adaptation supplied one.

Users pull cold out of the space immediately around themselves, sheathing their own bodies in ice or forcing it outward in short bursts. The reach is limited, so the power operates at arm's length rather than across a battlefield.

Sustained output punishes the body severely. Rei cannot hold the ability open for long stretches, and pushing past her ceiling risks frostbite spreading through her limbs and torso. Her core temperature falls sharply once she exceeds her limits, far enough that hypothermia becomes a real danger.

Supplementary material notes a temperament that travels with the genetics: carriers tolerate warm weather poorly and gravitate toward the cold. A separate power called Snowfall, which conjures a blizzard, is described as working along similar lines.

Rei's ice is precisely why Enji Todoroki sought her out for a Quirk Marriage, hoping the union would yield a child in whom her cold and his Hellflame fused perfectly. Fuyumi and Natsuo inherited the ice unchanged. Toya, the eldest, received an intensified form of his father's fire instead, along with his mother's resistance to cold and too little tolerance for his own heat, a mismatch that broke him; ice surfaced in his own arsenal only after a brush with death. Shoto, the youngest, finally became what Enji had wanted, since Half-Cold Half-Hot carries the strength of both sides while cancelling the weaknesses each has alone.

The first appearance of the power is a grim one. Rei freezes Shoto's scalded face after a breakdown drives her to pour boiling water on him. Years later, during Endeavor's clash with Dabi, she armors herself against the surrounding inferno and keeps the two men from launching skyward, with Fuyumi and Natsuo shielding themselves the same way as they try to bring their brother's temperature down.

All three take major burns holding that line, but their combined ice reroutes Dabi's self-destruction long enough for Shoto to arrive and finish it with a Phosphor-empowered Great Glacial Aegir. Shoto later concedes that acting by himself, he may well have fallen short.