Oslo

is King's pet Black Hound, an insanely vicious wild creature that will hunt enemies until it successfully kills them.

Appearance
Oslo is dog-like creature with dark purple fur, who is covered in scars, with his neck being the only area with white fur. Oslo has a fairly short tail, sharp and piercing teeth, and grows larger with it feels threatened, as all black hounds so. It shrinks into a small dog when not feeling threatened at all, with its scars not being visible when it is in the form of a small dog.

Personality
Oslo, just like all black hounds, is an insanely vicious that will not give up on a prey until it successfully kills it. However, Oslo appears to be quite submissive toward King, and acted like a normal puppy before them.

History
How Oslo met King and submissive toward him has not been revealed yet, but it was revealed that Oslo know King many years before he met the Seven Deadly Sins, in the Fairy Realm.

Capital of the Dead arc
Oslo was attacking and killed a Holy Knight apprentice Andre and his partner who were about to attack the Sins. Oslo was about to attack them but Ban and try to threaten the beast but he grew larger due to his ability but Meliodas used his sword to created a illusion of a very huge, fearsome, ethereal dragon-like creature which scared Oslo who trunk down and ran away. Oslo later return back to King his owner and after King first fight with Ban, King return embarrassed because Diane was there and he said she was so cute and told Oslo what to do but King and Oslo saw the Sins and they were trying to find a way to the Capital of the Dead and then a bunch of flowers were going wild and they disappeared along with King. For now Oslo is waiting for King to come back.

Kingdom Infiltration arc
King later summon Oslo through a portal that the latter made and introduced it to Diane and revealed Oslo ability to teleport and the fact he never bought him was that Oslo like pork. King told Oslo to teleport Diane to Liones but she was too big and King ordered Oslo to get bigger so he doesn't push Diane butt. As Diane was being attacked by the Holy Knights, Oslo felt Gilthunder Thunderbolt and end up getting damage up. King went to Oslo to see if he was alright, but manage to sent King to Liones to save Diane.

Abilities/Equipment
Oslo is very quick and powerful, which is seen when he quickly defeats two Holy Knight apprentices with ease. He also has the the ability to change his size depending on how threatened he feels. He grew very huge when Ban released a lot of killing intent toward him, and was later seen to be as small as a small dog when not threatened at all. Like all Black Hounds, Oslo have the unique ability which allows it to send anything it swallows to a completly different location.

King
King is Oslo's master and is very loyal to him.

Capital of the Dead arc

 * Meliodas vs. Oslo: Loss

Trivia

 * Oslo is the capital, and the most populous city in Norway.
 * Oslo favorite food is pork, which is the reason why he was never introduced to everyone in the Boar Hat.