Werebeaver Transformation

Legendary resistance [3/day]

Keen Hearing and Smell: The werebeaver has advantage on Wisdom (Perception) checks that rely on hearing or smell.

Blood Frenzy: Attacks of opportunity against the werebeaver have disadvantage. If the werebeaver moves to another target it did not already attack during this turn, it gains advantage against this creature.  

Rage (triggered when transforming): While raging, you gain the following benefits

• You have advantage on STR checks and STR saving throws.
• You have resistance to bludgeoning, piercing, and slashing damage
• Attacks are considered magical

Restauration: If it has been sprayed with any body fluid but not wounded by a silver weapon during the previous turn and it as at least 1HP, the werebeaver gains 4d10 + CON at the end of its turn.

Action Surge [1/rest] 

Multiattack: The werebeaver makes three attacks: one with its bite and two with its spear 

Bite. Melee Weapon Attack: +10 to hit, reach 5 ft., 1 target. Hit: 2d12 + 6 piercing damage. The target must then make a WIS save (DC 16) or use their reaction to move and make a melee attack against the closest target they can see.

Spear. Melee Weapon Attack: +10 to hit, reach 10 ft., 1 target. Hit: 1d6 + 6 piercing damage.

Poll arm master: When you take the Attack action and attack with only a glaive, halberd, quarterstaff, or spear, you can use a bonus action to make a melee attack with the opposite end of the weapon. This attack uses the same ability modifier as the primary attack. The weapon's damage die for this attack is a d4, and it deals bludgeoning damage

Poll arm master: While you are wielding a glaive, halberd, pike, quarterstaff, or spear, other creatures provoke an opportunity attack from you when they enter the reach you have with that weapon.

Spell Reflection [3/day]. If the werebeaver makes a successful saving throw against a spell, or a spell attack misses it, the werebeaver can choose another creature (including the spellcaster) it can see within 120 feet of it. The spell targets the chosen creature instead of the werebeaver. If the spell forced a saving throw, the chosen creature makes its own save. If the spell was an attack, the spell is rerolled against the chosen creature.

The werebeaver can take 3 legendary actions per turn from the list below. Legendary actions must be used at the end of someone else's turn, and only one at a time. 

Jump and attack (Costs 1 Action). After having taken damage from a ranged attack or spell, can jump behind the opponent and make a spear attack.

Tidal wave (Costs 2 Actions): Range 120ft: You conjure a massive wave of "water" that crashes down to an area you pick within range.
This area has a maximum dimension of 30 feet long, 10 feet wide, and 10 feet high.
All creatures within that area need to do a DEX saving throw (DC16). They take 4d8 bludgeoning damage and are knocked prone on a fail, or take only half the damage and are not knocked prone on a success.
Tidal Wave also extinguishes all the unprotected flames in the area and within 30 feet of that area.