This unnamed Boar is the pet of Halvor. It appears in both "Chapter 3: The Giantslayer" and "Hilda and the Faratok Tree".
The boar accompanies Halvor everywhere. Halvor can also ride the animal in battle, like he did when fighting Kald.
When Hilda and Halvor got into a sword fight, the boar tried to attack Hilda, but Twig jumped in between to defend his owner. After a brief fight, Twig tricked the boar into ramming headfirst against an apple tree, causing a load of apples to fall onto his head, knocking the boar unconscious.