Cloud allowed Oboro to create different-sized clouds, dense enough to be touched and even to hold up the weight of one or several people. These clouds could float in the air, so Oboro was capable of moving through the air by riding on them at great speed. The clouds could even store objects inside themselves.
When Oboro's corpse was stolen by All For One to be transformed into Kurogiri by Kyudai Garaki, the Quirk also underwent numerous modifications, used it as the base Quirk for Kurogiri's Warp Gate, which generates a dark fog that acts as a Portal but does not appear to retain the abilities of the original Quirk.
Oboro generally used his Quirk to move around, and thanks to the fact that the clouds can fly, he could easily overcome any obstacle. This allowed him, for example, to enter a building through the windows located in upper floors without problems, as he did to enter his class at the U.A., or when he infiltrated with Midnight in the room where the Robber Villain helded several hostages.
When facing a foe, the ability to fly and the great speed of the clouds gave Oboro great maneuverability, since it allowed him to dodge the enemy's attacks and strike him from blind angles by surprise. He could also generate billows to block the enemy's vision, or create a number of clouds to hide in one of them, using his gourd-like speaker to confuse the enemy, making him attack a cloud in which he is not in order to later ambush him from another.
The density of the clouds also allowed Oboro to use his Quirk to shield people under them, as he did to protect group of nursery kids from the debris of a falling building.