Witch's experiment

The Witch's Experiment is a shapeshifting monster fought near the end of the Witch's House quest. It has four forms, each of which must be fought consecutively, and each of which use Melee and have no drops.

Its forms are a level 19 Skavid, a level 30 Spider, a level 42 Bear, and finally a level 53 Wolf, each of which are purple recolours of the respective monsters.

Once you have defeated it, you may retrieve the ball. The experiment is described by Nora T. Hagg in her diary, where it appears to have been akin to a pet for her, as she is both angered and sorrowed at the loss of her precious "Fritz".

It can be fought in the Nightmare Zone after the quest is complete.

On both the normal and hard mode difficulty in the Nightmare Zone, the Experiment uses an ability that reduces combat stats, therefore, Overload potions are recommended.

Trivia

 * Each of the Experiments' forms are numbered in its respective forms. When it's a spider, it is called "Experiment (second form)". When it's a bear, it's called "Experiment (third form)". When it's a wolf, it's final form, it is called "Experiment (fourth form)". This doesn't apply to its skavid form however, it's simply referred to as "Experiment".
 * While the quest is active, players can take on the Experiment as many times as they wish. They simply have to leave and re-enter the shed and it will re-appear.