Were Possum

Lycanthropic Curse. Whenever the one holding this curse casts any spell, including cantrips, or does anything the DM deems stressful, roll a d20. On a 1, make a Constitution saving throw. The DC starts off at 10 and is automatically 25 when there is a full moon out. Upon each success, the DC increases by 1, and after a failure, the cursed creature becomes a Were Possum and the DC resets. 

Smol and Cute. The possum is considered a small creature, and has advantage on all Charisma checks from creatures that do not know it is not an actual animal.

Prehensile Tail. The possum can use its tail to grab something small and relatively light. It can also use this tail to help climb small trees or structures.

Keen Smell. The possum has advantage on Perception checks that rely on smell.

Venom Resistance. The possum has resistance to all Poison damage while in this form, and is immune to the Poisoned condition. 

While in Were Possum form, the cursed creature can cast any spells they have as normal, using their un-transformed Spell DC for saves. 

Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 1d6 + 4 piercing damage. Can use this attack twice during one action.

Return to Normalcy. In order to reverse the effects of the Lycanthropic Curse trait, the Were Possum must use an action to roll a Wisdom saving throw. The possum must not be under the effects of Play Possum. If in combat, the DC for this is 10 minus 1 per each round spent in possum form, and if not in combat, the DC is 15. Upon failure, the possum is too scared to revert and leaves behind a little pellet. Upon success, the creature transforms to no longer be a Were Possum and regains all of their actions/reactions (but not any used movement) as though it was the start of their turn.

Play Possum. The possum may use a reaction to fall prone, and appear still and rigid as if dead. While in this state, the possum is considered Paralyzed. If a creature wishes to detect if the possum is still living, they must succeed on a DC 15 Investigation check. The possum must use this trait immediately after dropping below half of its current max HP. When done in this way, the possum must use an action to regain consciousness. Otherwise, the possum may stop at any time as a free action.