Keychain | Studio Ghibli | Soot Sprite

The Soot Sprites (すすワタリ, Susuwatari, lit. "Travelling Soot"), also known as All Blacky (まっくろくろすけ, Makkuro-Kurosuke) are spirits that appear in the films My Neighbor Totoro and Spirited Away.

My Neighbor Totoro
They are small, round balls made from the soot that dwells in old and abandoned houses and leave black dirt in their wake. If the house becomes inhabited, they decide if the inhabitants are nice people. If they are, they will leave.

Spirited Away
According to Kamajī, Susuwatari [were] created by magic, and if they don't work diligently, the magic would dissolve, resulting in their disappear[ance].

The Soot Sprites (conjured from soot itself) are small, black, fuzzy creatures with spherical bodies and white eyes with black pupils. Their usual mode of transportation is levitating/hovering, but it is revealed in the film that they can extend black, wiry limbs (arms and legs) from their bodies to accomplish certain tasks (in this case, moving coal into the furnace) and can lift objects many times their own weight. They also dissolve into soot if crushed, but quickly reform themselves shortly after.

(from Fandom Ghibli Wiki)