Calamity Beast

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

Magic Resistance. The Beast has advantage on saving throws against spells and other magical effects.

Tough Plates: Has 2 AC numbers, 23 and 25, below 23 does not hit 23-25 hits but does half damage above 25 fully hits

Crystal Attacks: Upon a creature being hit it gains 1 stack of crystal growth upon 5 being obtained by a creature all will detonate on all enemy creatures dealing 1d12+2 psychic per crystal the creature that it detonated on must roll a CHA save or get charmed for 3 turns.

Pure Strength: When the Beast hits someone all their immunities are turned into resistances all resistances are turned into -2 damage.

Hive Mind: For each friendly or charmed creature in the fight the Beast regains 1d10+1 HP every other turn.

Save DC: 22

Multi-Action: The Beast has 2 actions to use.

Screech. (Costs 2 actions) All enemy creatures within 600ft must roll a CHA save on a fail they get charmed for 1 round also summons 5 infected creatures to its aid cooldown of 4 rounds.

Stomp. Melee weapon attack: +20 to hit, 30ft circle AOE, Hit: (3d8+10) Force damage. All who get hit must roll a DC 18 STR save or get knocked back 50ft and knocked prone.

Spike Call. Ranged Weapon Attack: DEX save, range 240ft circle AOE. Hit:  (3d6+5) Piercing damage spikes rain down onto everything in the radius next round on its turn the spikes explode refer to the stats above for the rolls required for this follow-up.

Corrupt Magic. Ranged Weapon Attack: +18 to hit, 6 Targets (can be the same multiple times each hit causes 1 stack of Crystal Growth), Hit: (1d6+2) Force damage. 6 Huge purple magic missiles come out and go towards the targets (not guaranteed hits because game balance)

Pillar Growth: Only usable if a creature is above it or on its back/side upon use all creatures 40ft above or on its side or back must roll a DC 20 DEX save or be thrown 30ft and take 3d6+4 bludgeoning.

Piercing Gaze: (does not trigger crystal attacks) Ranged Weapon Attack: DC 19 WIS save, range Wherever it can see. 1 target Hit: (2d12+6) Psychic damage

Sympathy Exploit: Trigger: On getting hit, the one who hit the Beast must roll a WIS save on a fail they deal half damage with all attacks until the effect ends. On each of the targets turns it can roll the wisdom save again as a free action once it succeeds it cannot suffer the same effect for 2 turns.

The Beast can take 2 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 Beast regains spent legendary actions at the start of its turn.

Crystal Breath (Costs 2 Actions). The creature breaths air laced with crystal, all creatures within 240ft cone gain 3 stacks of crystal growth.

Wind Roar (Costs 1 Actions). All creatures in a 150ft radius must roll a STR save or get knocked back 90ft.