Bateth

Plague. The Bateth can chose to heal  3d12 hit points every round during its action, when it heals everyone in a square 30ft in width and 30ft in length measuring 40 in the air, must make a constitution saving throw (DC 15) or take 1d10 hit point of poison damage. The target must take this saving throw or continue to take this amount of damage. Target that cannot be affected by disease are unaffected.

Deathly Stab: The Bateth can chose to move ten more feet in order to reach a target and attack with its Greatsword and have advantage on the attack roll. If the attack hits the target 

Multiattack. The Bateth makes three attacks with its tail and two with its Arcane greatsword.

Arcane Greatsword. Melee Weapon Attack: +4 to hit, reach 15ft., 1 target. Hit: 3 (2d12 + 7) [slashing] damage. If the attack roll its the target must make a DC 15 constitution saving throw or take 4d10 psychic damage and be knocked prone. If the target is revived its has disadvantage on all attacks made against the Bateth. 

Shield Crush: Melee Weapon Attack:  +6 to hit,  15  foot box, Hit: 3 (5d4+ 7) bludgeoning damage . The target must make a DC:13  dexerity saving throw or take  damage labeled above. 

Tail Strike:  Unarmed strike: +8 to hit, Hit  3 (1d8+2) bludgeoning damage. 

Inch Of Life. If a target in a cone of 15 ft in circumference and moves more than 5 feet, the Bateth can make an Inch Of Life reaction, if the attack hits the creature makes an attack roll and attempts to grapple the target digging its greatsword into the heart. The target takes (3d12+7) damage.

The bateth can take 1 legendary action during its turn and can chose from the two  listed below. 

Mind Barrier (Costs 1 Actions). The Brain of the target pops a blood vessel and take (6d10+4) psychic damage.

Healing Vibration (Costs 2 actions). After any failed saving throw or after taking damage The Bateth vibrates and repairs itself by (3d20+7) hits points.