Allmother of the Axolotl

Amphibious. The Allmother can breathe air and water.

Freedom of Movement. The Allmother ignores difficult terrain, and magical effects can't reduce its speed or cause it to be restrained.

Legendary Resistance (3/Day). If the Allmother fails a saving throw, it can choose to succeed instead.

Siege Monster. The Allmother deals double damage to objects and structures.

Axolotl Mother. Won't attack any axolotl or creatures loved by the axolotl.

Multiattack. The Allmother can use its Frightful Presence. It then makes four or two attacks: one with its tail, two with its arms, one with its head or an Waterball instead of the arms and head.

Tailsweep. Melee Weapon Attack: +18 to hit, reach 60 ft., area 200x100 feet. Hit: 40 (4d10 + 10) [bludgeoning] damage. If the target is a creature, it must succeed on a DC 20 Strength/Dexterity saving throw or be knocked prone and take full damage.

Headbutt. Melee Weapon Attack: +18 to hit, reach 30 ft., one target. Hit: 24 (4d6 + 10) [bludgeoning] damage. 

Armsweep. Melee Weapon Attack: +18 to hit, reach 30 ft., area 20x10 feet. Hit: 24 (4d6 + 10) [bludgeoning] damage. 

Waterball. RangedWeapon Attack: +16 to hit, range 30/600 ft., 1 target. Hit: 56 (7d8 + 20) [cold] damage. If the target is a non-aquatic creature, it must succeed on a DC 20 Strength/Dexterity saving throw or be knocked prone and take full damage. An aquatic creature always takes half damage and isn't prone.

Water Wave(Only in Water). As a reaction it can push away creatures 30 feet away in a 20 feet radius from the moving creature, which tries to move in its range.

The Allmother can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The Allmother regains spent legendary actions at the start of its turn.

Axolotl Regeneration(Costs 3 Legendary Actions). Heals for 300 Health every 1d6 rounds.

Tsunami (Costs 2 Legendary Actions, Only in Water). Creates a Tsunami Wave which is 300 feet high and 900 feet long and sweeps away everyone who doesnt succeed a DC 25 Dexterity/Strength saving throw.

Axolotl Creation(Costs 1 Legandary Actions).  She can create about 4d6 Small Axolotl who fight for her every 1d6 rounds.