Baldur

Behaviour and Tactics
Rolls into a ball and propels itself towards The Knight, bouncing off walls and other Baldurs. After a short time it will uncurl and reorient itself to face the Knight again.

Jump over it when it gets close and strike from above while doing so. Alternatively, using Quick Slash or Heavy Blow will continually knock it back before it can make contact.

Trivia
On the official website, it is referred to as Scrundling Propede (infant):

Although the shells of these youngsters are not thick enough to protect them from predators, they are still able to defend themselves if pressed. Бальдр Baldur