Wilbur

Wilbur is a Beast monster boss that is always fought together with the Swine Prince in the Warrens.

History
Wilbur is a small and skittish Swinefolk that has somehow become the companion and controller of the frighteningly powerful and stupid Swine Prince. In battle, the Swine Prince takes orders from Wilbur and protects him, falling into fits of blind rage whenever Wilbur is hurt or killed. As of yet there's no canonical story of Wilbur's background and of how he got to this position, but it can be safely assumed that Wilbur and the Swine Prince share some sort of connection, perhaps even prior to their cruel transformations.

Behaviour
During battle, Wilbur will use the attacks End This One or End These Two on one or two of your heroes. This marks your heroes for extra damage from the Swine Prince's attacks, as well as targets your specific heroes to the Swine King's attacks.

Wilbur can be killed to stop the marking of your heroes, however, this will result in the Swine Prince attacking all of your heroes every turn.

After the Swine Prince is defeated, the heroes will also have to defeat Wilbur (running however after the prince has fallen but before Wilbur has been defeated will still result in the quest being completed.) Wilbur will use Squeal, which does one to two points of damage, but mainly inflicts Stun on your heroes.

There is an important difference between the Apprentice Level fight iteration of Wilbur and the other counterparts, such as follows: At Veteran Level, you will be introduced to his Bit'o Squeal, which significantly makes the fight harder by stunning your heroes at the start of every turn. Since he has 2 turns, the second one is reserved for either marking or squealing, according to his position.
 * 1) Wilbur will not use Bit'o Squeal on the Apprentice Level boss fight, despite having it as an ability, it will either mark your heroes or squeal at them if in the first position.
 * 2) Wilbur will only have one turn, which will be spent as mentioned above marking or squealing.

Furthermore, at the Champion level fight, Wilbur will have a 3x chance of using "End These Two" instead of "End this One". Therefore, expect and be prepared against heavy AOE damage.

Strategy
It's best not to inflict damage upon Wilbur at all before the Swine Prince is slain. However, skills that stun without causing damage (such as Flashbang, Blinding Gas, or Disorienting Blast) won't trigger a retaliation from the Swine Prince, allow you to prevent Wilbur from marking or stunning your heroes for a turn.
 * Disorienting Blast is especially useful for this fight: not only does it stun Wilbur but also moves him forward, preventing him for marking your heroes at all next turn. Although Wilbur's attacks will move him backward again, it's possible to keep hitting him with the ability every other turn to (mostly) prevent him from landing any marks.
 * The Arbalest's Rallying Flare can dispel Wilbur's marks, preventing the Swine Prince from using his most powerful abilities. Consider giving her trinkets that boost stun resist, however - if Wilbur stuns her, you'll have no way to dispel the marks and the Prince might land a devastating crit.
 * Because the Champion Level fight involves a lot of damage to your front lines, it should be well-advised to bring tanky heroes to the front row, as Wilbur will mostly mark them instead of the other positions (be aware that this can still happen 25% of the time).

Trivia

 * Wilbur's name may be a reference to Charlotte's Web, where the main character is a pig of the same name. However it is more likely that Wilbur is inspired by Wilbur Whateley from H.P. Lovecraft's story the Dunwich horror. Wilbur was the more "Human" of two brothers, sons of Yog-Sothoth. His sibling was the titular Dunwich horror, and he had the role of caring for the monster and keeping it contained until the time when it would be unleashed. When Wilbur is killed in the story, the monster goes on a rampage. This closely mirrors the relationship between the small, "normal" looking Wilbur, and the monstrous Swine Prince, as if Wilbur is harmed or killed, the Swine Prince will become far more dangerous and relentless in its attacks.
 * Being killed by Wilbur will unlock a hidden achievement.