|How many friends have I killed today?|
If the wearer is struck for damage (other than falling damage), the magic of the cloak will cause it to become unremoveable and in addition each point of damage gives a 1 in 10 chance (non-cumulative from hit to hit) of causing the wearer to transform into a large and very angry bear - specifically the one that donated its hide to make the cloak. The bear will act pretty well as a bear and fight anything nearby, starting with anything associated with the damage that set the transformation off. After that it will simply turn on the nearest animate creature or object in reach/sight. The bear can only be struck magical or silver weapons and can continue to fight after 0hp in the same way as a true bear.
This process will continue until ten combat rounds have passed without the bear being hit for damage or doing any damage. At this point the transformation will wear off and the owner of the cloak will be found standing in it, probably otherwise naked and with their possessions scattered around the area (consult the lycanthropy rules on DMG p23 for effects of wearing armour during the change).
If the wearer is struck for damage but does not eventually transform, the enchantment on the clasp will allow the cloak to be removed after a similar ten rounds wherein no damage is suffered or dealt.
The specific bear form is one of the following:
When the cloak is placed or found, the DM should roll the hit points of one of these bear types and retain these. Damage done to the bear comes off these and heal at a rate of three per day if the bear does not manifest or just one point if it has done so within the previous 24hrs.
If the bear is killed in combat the cloak will not activate again for a full month, at which point the bear will be at its full hit points again.
On returning to normal form the owner will have lost half as many hit points as the bear did, and may therefore be dead.
The magic of the cloak will detect as alteration and necromancy.
xp: 200+100/HD (ignore +'s)