Imprisoned Dog
On occasion the Travesty will drop an oddly colored Power Crystal with what appears to be a dog inside. The one who uses this item will shatter it, releasing the creature which will instantly bond to him/her as a pet.
Although the imprisoned version shares the vital statistics of any other Dog, it has one extra ability - It will, on occasion, randomly shape shift into the form of any creature within a short range. It will only revert to its original appearance if killed or stabled.
When mimicking a character, the Imprisoned Dog will also create copies of the equipment worn. The new items will be of the same color as the originals but lack any additional properties.
As an example, if a character holding The Redeemer is cloned, the dog will hold a standard Paladin Sword of the same color instead. It may then use this item in combat, and also gains resistances from any armor it should obtain (these resistances are not lost should it change to a non-character type form).
Unlike a Changeling, the creature cannot mimic the skills of characters. It is currently unknown as to whether the creature is capable of training extra combat skills through the use of weapons and shields. It is incapable of firing a bow as it can hold no ammo.
On release, Imprisoned Dogs disappear.
Exploit
At some stage or other there was a bug that allowed players to duplicate items using an Imprisoned Dog. This author is unsure as to how this was done, which items were duped and when it was eventually patched out, but I'd assume pets holding Paladin Swords were disarmed and then robbed.
Although Imprisoned Dogs in Human/Elven forms do have backpacks which can be snooped, they can hold no items in them and cannot be disarmed.