Boss Encounter 19 - lvl 5 to 10

1x Kirin Large celestial , unaligned
Armor Class 17 Natural Armor Hit Points (15d8 + 125) Speed 60 ft.
STR 21 (+5) DEX 16 (+3) CON 16 (+3) INT 19 (+4) WIS 20 (+5) CHA 20 (+5)
Skills Insight +9, Perception +9, Religion +8 Damage Immunities Lightning Condition Immunities Paralyzed Senses Blindsight 30 ft, Darkvision 120 ft, Passive Perception 19 Languages all, telepathy 120 ft. Challenge 12 (8,400 XP) Proficiency Bonus +4
Control Lightning. The kirin can choose any location within 30 feet of it as the starting location of the lightning bolt spell.
Innate Spellcasting. The kirin's innate spellcasting ability is Wisdom. It can innately cast the following spells (spell save DC 17), requiring no material components:
At will: control weather, expeditious retreat, gust of wind, see invisibility
Legendary Resistance (3/Day). If the kirin fails a saving throw, it can choose to succeed in stead.
Magic Resistance. The kirin has advantage on saving throws against spells and other magical effects.
Magic Weapons. The kirin's weapon attacks are magical.
Spellcasting. The kirin is a 18th-level spellcaster. Its spellcasting ability is Wisdom (spell save DC 17, +9 to hit with spell attacks). It regains its expended spell slots when it finishes a short or long rest. It knows the following spells:
Cantrips (at will): light, shocking grasp, thaumaturgy, thunderclap 1st-5th level (4 5th-level slots): call lightning, destructive wave, elemental bane (lightning), lightning bolt, storm sphere, thunder step, thunder wave
Actions Multiattack. The kirin makes three attacks: two with its hooves and one with its horn.
Hooves. Melee Weapon Attack. +9 to hit, reach 10 ft., one target. Hit: (2d4 + 5) bludgeoning damage.
Horn. Melee Weapon Attack. +9 to hit, reach 5 ft., one target. Hit: (2d8 + 5) piercing damage.
Legendary Actions The kirin 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 creatures turn. The kirin regains spent legendary actions at the start of its turn.
Detect. The kirin makes a Wisdom (Perception) Check.
Smite. The kirin makes a hoof attack or casts thunderclap.
Move. The kirin moves up to its half speed without provoking opportunity attacks.