Bean-nighe

Limited Magic Immunity. The creature, being a creature of pure mythical power, has limited immunity to magic, and spells. Any spell of 3rd level, or lower has no effect on it.

Legendary Resistance. If the creature fails a saving throw, she can instead choose to succeed. This feature can only be used three times daily. (3/day)

Commune with The Wild. The creature can speak to plants and animals as if the shared a language.

Everlasting Breathe. The creature does not need to breathe.

Spell casting. Titania is a 20-level spellcaster. Its spellcasting ability is Charisma (spell save DC 25, +15 to hit with spell attacks). Titania has following spells prepared: 

Cantrips (at will): Druidcraft, Create Bonfire, Control Flames, Dancing Lights, Eldritch Blast, Frostbite, Gust, Shape Water, Mold Earth, Thorn Whip.
1st level (8 slots):  Bless, Chaos Bolt, Charm Person, Command, Sleep, Tasha's Hideous Laughter, Create or Destroy Water

2nd level (6 slots): Animal Messenger, Blindness/ Deafness, Crown of Madness, Shatter, Summon Bestial Spirit.

3rd level (6 slots): Blink, Counter Spell, Wall of Water

4th level (6 slots): Banishment, Confusion, Polymorph.

5th level (6 slots): Dawn, Dominate Person, Telekinesis, Maelstrom

6th level (4 slots): Arcane Gate, Sunbeam, Wall of Ice

7th level (4 slots): Plane Shift, Prismatic Spray, Reverse Gravity, Whirlwind

8th level (2 slots): Tsunami, Control Weather

Multi Attack. The creature can make two spell attacks or four melee attacks.

Hagged Claws.  Melee Weapon Attack: +14 to hit, reach 5 ft., 1 target. Hit: 15 (1d8 + 10) slashing damage, plus 15 (5d6) magical damage.

Any creature that is struck with the claws must make a WIS. saving throw (DC13) or be sent into a fit of untamable emotion until their next turn. Roll a d4 to see which emotion. The saving throw can be redone at the start of the creature's turns, and on a success, the effect ends, and the creature becomes immune to this effect for the next 24 hours.

1. Rage: Rage blurs their vision and clouds their judgement. They are compelled to attack the closest creature, friend or foe. If a water source is nearby, they are compelled to try and drown the creature.

2. Sadness: Sad thoughts drown their mind in woe. They are knocked prone, and cannot use their action or bonus action to attack.

3. Joy: Joyous thoughts fill the creature's mind, and they can't even think of hurting anything. They become a complete pacifist, and cannot attack any creature, by any means.

4. Dread: Thoughts of pure fear course through their mind. All attack rolls are made at a disadvantage, and the creature's movement is reduced to 0ft.

Enter the description for how bonus actions work for your monster here.

Perfect Parry. When attacked by a melee attack, the creature rolls a d20+13, and if the roll is equal to or greater than the attack roll, it evades it, taking no damage.

Wash Away. When attacked with a spell that does thunder or cold damage, the creature lets out a horrifying shriek before ejecting a powerful wall of water from its mouth. All creatures must make a DC15 strength save or be knocked prone.

Being one of the most powerful of all the creatures in the Scot Lands, it has 5 legendary actions.

Lesser Spell Casting (Costs 1 Actions). The creature casts a 4th level spell or lower.

Greater Spell Casting (Cost 2 Actions). The creature casts a 5th level spell or lower. 

The Queen's Wrath (Cost 1 Action). The creature makes 3 attacks with their claws.

If the creature dies, the following happens.

Droplet (Costs 1 Action).  Upon death, the creature fades into a single drop of water. This water is immune to all damage and will exist for eternity.