Quirk Bestowal

Quirk Bestowal ("個性"付与) was the Quirk used by Yoichi Shigaraki and the other users of the One For All Quirk.

After All For One forcibly transferred a power stockpiling Quirk to Yoichi, Quirk Bestowal merged with the other Quirk and resulted in the creation of One For All.

Description
This Quirk has no power other than it could be transferred from one person to another. Unlike most other Quirks, which usually manifest before the age of four, Quirk Bestowal did not make itself known for most of Yoichi's life, leading to the false belief that he was Quirkless. To transfer this Quirk, the user has to willingly pass it to another through DNA, such as by the recipient ingesting a strand of hair or a drop of blood.

It is the only known Quirk that cannot be stolen by All For One. As Quirk Factor types tend to run in families, it's likely that Quirk Bestowal always had the ability to assimilate or absorb the Quirks it came into contact with through transference, much like how his brother's Quirk could also take in multiple Quirks (though by directly and consciously stealing them). This is what probably also allowed his Quirk to absorb and combine with the power stockpiling Quirk, creating One For All.